For Iran, Enriching Uranium Only Gets Easier


- By WILLIAM J. BROAD - March 8, 2010 - The New York Times

In the Iranian desert, at a sprawling industrial site ringed by barbed wire and antiaircraft guns, a shift in the enrichment of uranium is producing global jitters because it could shorten Iran’s path to the acquisition of nuclear weapons.

It is also illustrating one of the peculiarities of uranium enrichment, a version of the rich getting richer, really fast. The tricky process accelerates as it moves ahead. “The higher the concentration, the easier it gets,” said Houston G. Wood III, a professor of mechanical and aerospace engineering at the University of Virginia who specializes in nuclear enrichment. The process is, as scientists like to say, nonlinear.

Four years ago, Iran began enriching uranium on an industrial scale with centrifuges, machines that spin extraordinarily fast to separate uranium 235 from the more common form of the element, uranium 238. Uranium 235 is a natural rarity that splits easily in two, or fissions, in bursts of atomic energy, either in a reactor or a bomb. Reactor-grade fuel is usually defined as uranium 235 of about 4 or 5 percent, and bomb-grade as 90 percent or higher.

The desert complex, the Natanz nuclear facility, raised the level of uranium 235 to roughly 4 percent from its natural concentration of 0.7 percent. Over time, the facility produced two tons of concentrated material, enough, if further enriched, to make about two atom bombs.

Then, on Sunday, Feb. 7, Iran announced it would begin enriching its stockpiled uranium to 20 percent — ostensibly to make fuel for a research reactor in Tehran. Nuclear experts said that although this might sound like a leap, moving to 20 percent from 4 percent was actually a fairly easy step — not at all as demanding and time consuming as raising the level to 4 percent from 0.7 percent. And the ease of further enriching uranium once it is already enriched made the world take notice.

The new enrichment effort began Tuesday, Feb. 9. Three days later, France, Russia and the United States criticized Iran’s move as an “escalation.” In a letter to the International Atomic Energy Agency, an arm of the United Nations in Vienna, the three United Nations ambassadors from those countries said the heightened effort raised “new concerns about Iran’s nuclear intentions.”

A senior Obama administration official, speaking on the condition of anonymity, told reporters on Feb. 18 that the enrichment step and related Iranian moves were clear provocations. “This program,” the official said, “is heading more and more in the direction of seeking a weapons capability.”

In scientific terms, rather than political ones, the issue is “nonlinearity,” a word almost as scary to nonscientists as highly enriched uranium is to the International Atomic Energy Agency. The definition is fairly simple, however. In a nonlinear process, a particular input produces an output that is disproportional in size, either big or small. The weather is conspicuously nonlinear, with small changes in one area producing deadly storms elsewhere. So are earthquakes and explosions. The word describes inequality in cause and effect.

A practical illustration of nonlinearity is that Iran — or any other nuclear hopeful — needs increasingly few centrifuges to make uranium 235 increasingly potent. For instance, one industry blueprint features 3,936 centrifuges for enriching up to 4 percent, 1,312 centrifuges to 20 percent, 546 centrifuges to 60 percent and just 128 centrifuges to 90 percent — the level needed for a bomb.

The reason is that “you’re moving a lot more material at lower levels of enrichment,” said David Albright, president of the Institute for Science and International Security, a private group in Washington that tracks nuclear proliferation and disclosed the blueprint. “It’s the reduction of the material” that makes the process gradually easier.

Centrifuges that whirl small amounts of gaseous uranium at high speeds are used to separate the element’s different forms, or isotopes, starting with material that consists of 99.3 percent of the heavier uranium 238. At each step, more of the heavy uranium is removed and the remaining material, now with a higher concentration of the lighter isotope, goes through the centrifuge process again.

Uranium ore has about 140 atoms of the heavy isotope for every light one, and separating the two takes a lot of spinning. By the time the enrichment process has reached 4 percent, it has successfully removed some 115 of the heavy atoms.

To get from there to 20 percent — the enrichment goal of the Iranians — the spinning centrifuges need remove only 20 more of the heavy atoms. And from there it is even easier to jump to 90 percent, bomb grade, by removing four or so additional heavy atoms. That is what worries many countries.

In the desert, at the Natanz complex, Iran presented atomic inspectors with evidence that it had succeeded in enriching some of its 4 percent uranium to 20 percent, the United Nations agency said in a Feb. 18 report. But American and European officials said the amounts were small so far.

Originally, Iran enriched its uranium to 4 percent with thousands of centrifuges in two cavernous underground halls roughly half the size of the Pentagon. The center of its new effort, according to the atomic agency, is a facility at Natanz known as the pilot plant, where Iran currently has 164 centrifuges spinning. Even with the aid of nonlinearity, that number is insufficient to enrich much uranium quickly.

In interviews and briefings, officials in Washington and diplomats in Europe said the pilot plant could make perhaps three kilograms, or about seven pounds, of 20 percent fuel per month. At that rate, they added, making enough to power the research reactor in Tehran would take five to seven years. But the reactor has only months to go before it could run out of fuel, they estimated.

The experts said the leisurely enrichment pace suggested that Iran’s declared goal was disingenuous and that its real motive was simply to escalate its defiant brinkmanship and up the ante in global negotiations over its nuclear program. Moreover, the enriched material must be turned into reactor fuel rods — a process that many experts doubted Tehran could master.

“We do not believe that Iran has either the technical knowledge or the intellectual property rights” to make the fuel rods, said Catherine Ashton, the European Union’s high representative for foreign affairs and security policy.

Iranian officials have all but admitted that the aim of the enrichment move — at least in part — is to strengthen its negotiating stance. Last week, when reporters asked Ali Asghar Soltanieh, Iran’s ambassador to the International Atomic Energy Agency, when the country expected to produce the fuel assemblies, he professed to have no idea.

He added, “We have opened a window of opportunity for the others to prove their political will to come and to have a deal on the nuclear fuel.” For months, Iran and the West have negotiated unsuccessfully to have Iran’s 4 percent uranium sent abroad for processing into reactor rods. The West wants the material out of Iran to preclude its transformation into bomb fuel.

Since 2006, the United Nations Security Council has repeatedly called on Iran to halt its uranium enrichment. Washington and its allies say that Tehran is seeking the ability to make nuclear weapons, a charge it strongly denies.

The Institute for Science and International Security, in a March 3 report, called Iran’s enrichment to 20 percent “particularly troubling.” As early as next year, it said, Iran could accumulate enough material to take the next step on the path of centrifuge concentration and make bomb-grade fuel. If Iran fed the 20 percent material back into thousands of spinning centrifuges at its main plant, the institute said, it could make sufficient fuel for a weapon “within a month.”

Iran’s sprawling enrichment plant at Natanz currently houses more than 8,000 centrifuges and is designed to hold 54,000 — the number is that large because of Iran’s ostensible goal of supplying reactors with tons of fuel.

Another worry for the West is whether Iran is developing a new clandestine site to further enrich its uranium. Last September, President Obama disclosed the existence of a half-built plant buried inside a mountain near the holy city of Qum. The plant is designed to hold 3,000 centrifuges, but experts said its unveiling had ruined its original purpose as a secret site.

Iran is now disconnecting hundreds of centrifuges at the main plant at Natanz, according to the atomic inspectors. Experts were unsure why. The move could signal technical troubles or new plans.

The institute, in its report, suggested that “Iran could be in the process of moving at least some of these centrifuges elsewhere,” perhaps to new clandestine sites. Iran last year announced plans to build 10 centrifuge plants underground to protect them from aerial attack. Experts agreed that it stood little chance of making 10 plants, but might succeed in building 1 or 2.

All told, there are 20 operating enrichment plants in the world, according to a recent study by Oak Ridge National Laboratory in Oak Ridge, Tenn.

Nuclear specialists said that the vast majority of those plants — unlike Iran’s — enrich their uranium to no more than 4 or 5 percent. Despite the technical ease of further enriching uranium into fuel for a bomb, said Mr. Albright, the Institute for Science and International Security’s president, “there are very few that go to weapon grade.”

C.I.A. Secrets Could Surface in Swiss Nuclear Case


- By William J. Broad and David E. Sanger - December 23, 2010 - The New York Times

A seven-year effort by the Central Intelligence Agency to hide its relationship with a Swiss family who once acted as moles inside the world’s most successful atomic black market hit a turning point on Thursday when a Swiss magistrate recommended charging the men with trafficking in technology and information for making nuclear arms.

The prospect of a prosecution, and a public trial, threatens to expose some of the C.I.A.’s deepest secrets if defense lawyers try to protect their clients by revealing how they operated on the agency’s behalf. It could also tarnish what the Bush administration once hailed as a resounding victory in breaking up the nuclear arms network by laying bare how much of it remained intact.

“It’s like a puzzle,” Andreas Müller, the Swiss magistrate, said at a news conference in Bern on Thursday. “If you put the puzzle together you get the whole picture.”

The three men — Friedrich Tinner and his two sons, Urs and Marco — helped run the atomic smuggling ring of A. Q. Khan, an architect of Pakistan’s nuclear bomb program, officials in several countries have said. In return for millions of dollars, according to former Bush administration officials, the Tinners secretly worked for the C.I.A. as well, not only providing information about the Khan network’s manufacturing and sales efforts, which stretched from Iran to Libya to North Korea, but also helping the agency introduce flaws into the equipment sent to some of those countries.

The Bush administration went to extraordinary lengths to protect the men from prosecution, even persuading Swiss authorities to destroy equipment and information found on their computers and in their homes and businesses — actions that may now imperil efforts to prosecute them.

While it has been clear since 2008 that the Tinners acted as American spies, the announcement by the Swiss magistrate on Thursday, recommending their prosecution for nuclear smuggling, is a turning point in the investigation. A trial would bring to the fore a case that Pakistan has insisted is closed. Prosecuting the case could also expose in court a tale of C.I.A. break-ins in Switzerland, and of a still unexplained decision by the agency not to seize electronic copies of a number of nuclear bomb designs found on the computers of the Tinner family.

One of those blueprints came from an early Chinese atomic bomb; two more advanced designs were from Pakistan’s program, investigators from several countries have said.

Ultimately, copies of those blueprints were found around the globe on the computers of members of the Khan network, leading investigators to suspect that they made their way to Iran, North Korea and perhaps other countries. In 2003, atomic investigators found one of the atomic blueprints in Libya and brought it back to the United States for safekeeping.

Mr. Müller, the Swiss magistrate, investigated the Tinner case for nearly two years. He said Thursday that his 174-page report recommended that the three men face charges for “supporting the development of atomic weapons” in violation of Swiss law.

They are accused of supplying Dr. Khan’s operation with technology used to make centrifuges, the machines that purify uranium into fuel for bombs and reactors. Dr. Khan then sold the centrifuges to Libya, Iran and North Korea and perhaps other countries.

Mr. Müller’s recommendation comes as a new book describes previously unknown details of the C.I.A.’s secret relationship with the Tinners, which appears to have started around 2000.

The book, “Fallout,” by Catherine Collins and Douglas Frantz, scheduled to be published next month, tells how the C.I.A. sent the men coded instructions, spied on their family, tried to buy their silence and ultimately had the Bush administration press Switzerland to destroy evidence in an effort to keep the Tinners from being indicted and testifying in open court.

Ms. Collins is a freelance writer and investigator, and her husband, Mr. Frantz, is a former investigations editor for The New York Times and a former managing editor of The Los Angeles Times. He currently works on the staff of the Senate Foreign Relations Committee.

The C.I.A. has never commented on its relationship with the Tinners. But the story has leaked out, in bits and pieces, after news reports of Dr. Khan’s illicit atomic sales forced Pakistan’s government to expose the atomic ring and place Dr. Khan under house arrest. But Pakistan never allowed him to be interrogated by the C.I.A. or international nuclear inspectors, perhaps out of fear that he would implicate other Pakistani senior officials.

As a result, there has never been a full accounting of his activities, few of his associates have been tried or jailed, and there are strong indications that some of his suppliers are still operating.

But if the Pakistanis were worried about revelations surrounding Dr. Khan and whom he might have worked with in the Pakistani military and political hierarchy, the C.I.A. was worried about the Tinners.

The new book says the Bush administration grew so alarmed at possible disclosures of C.I.A. links to the family that in 2006 Secretary of State Condoleezza Rice lobbied Swiss officials to drop their investigation.

The book says the C.I.A. broke into a Tinner home in 2003 and found that the family possessed detailed blueprints for several types of nuclear bombs.

Paula Weiss, a spokeswoman for the C.I.A., declined to comment, and lawyers for the Tinners did not immediately respond to requests for comment. The Tinners have said that they were not aware that the equipment they supplied was intended for nuclear weapons projects.

Based on Swiss investigators’ findings, the book suggests that the bomb designs may have spread to a half dozen outposts of Dr. Khan’s empire around the globe — including Thailand, Malaysia and South Africa — and sharply criticizes the C.I.A. for leaving those plans in the hands of people suspected of being nuclear traffickers.

In late 2007, the Swiss government, under strong American pressure, decided to drop legal proceedings on espionage charges against the Tinners and other charges against a number of C.I.A. operatives who had operated on Swiss soil in violation of the country’s laws.

In early 2008, the more limited investigation on trafficking charges inched forward with great difficulty because the Swiss government — again at the behest of United States officials — had destroyed an enormous trove of computer files and other material documenting the business dealings of the atomic family. That action led to an uproar in the Swiss Parliament.

But in 2008 Swiss investigators discovered that 39 Tinner files scheduled for destruction had been overlooked, giving the authorities fresh insights into the ring’s operation — and new life for the legal case.

In his news conference on Thursday, Mr. Müller harshly criticized the Swiss government for having “massively interfered in the wheels of justice by destroying almost all the evidence.” He added that the government had also ordered the federal criminal police not to cooperate with his investigation.

If the Tinners are formally charged and their case goes to trial in Switzerland, they face up to 10 years in prison if they are found guilty of breaking laws on the export of atomic goods. All three men spent time in Swiss jails pending the outcome of the espionage and trafficking inquiries. The time they have already spent in jail would count toward any possible sentence.

In early 2009, Marco Tinner was freed after more than three years of investigative detention, and his brother Urs was released in late 2008 after more than four years in jail. Their father, Friedrich, was released in 2006.

Mr. Müller recommended that, in addition to charges of atomic smuggling, Marco Tinner should be accused of money laundering.

The Swiss attorney general is now studying the magistrate’s report and will decide next year whether to file charges against the Swiss family of atomic spies and entrepreneurs.


David Jolly contributed reporting from Paris.


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U.S. Enriches Companies Defying Its Policy on Iran


- By JO BECKER and RON NIXON - Published: March 6, 2010 - The New York Times

The federal government has awarded more than $107 billion in contract payments, grants and other benefits over the past decade to foreign and multinational American companies while they were doing business in Iran, despite Washington’s efforts to discourage investment there, records show.

That includes nearly $15 billion paid to companies that defied American sanctions law by making large investments that helped Iran develop its vast oil and gas reserves.

For years, the United States has been pressing other nations to join its efforts to squeeze the Iranian economy, in hopes of reining in Tehran’s nuclear ambitions. Now, with the nuclear standoff hardening and Iran rebuffing American diplomatic outreach, the Obama administration is trying to win a tough new round of United Nations sanctions.

But a New York Times analysis of federal records, company reports and other documents shows that both the Obama and Bush administrations have sent mixed messages to the corporate world when it comes to doing business in Iran, rewarding companies whose commercial interests conflict with American security goals.

Many of those companies are enmeshed in the most vital elements of Iran’s economy. More than two-thirds of the government money went to companies doing business in Iran’s energy industry — a huge source of revenue for the Iranian government and a stronghold of the increasingly powerful Islamic Revolutionary Guards Corps, a primary focus of the Obama administration’s proposed sanctions because it oversees Iran’s nuclear and missile programs.

Other companies are involved in auto manufacturing and distribution, another important sector of the Iranian economy with links to the Revolutionary Guards. One supplied container ship motors to IRISL, a government-owned shipping line that was subsequently blacklisted by the United States for concealing military cargo.

Beyond $102 billion in United States government contract payments since 2000 — to do everything from building military housing to providing platinum to the United States Mint — the companies and their subsidiaries have reaped a variety of benefits. They include nearly $4.5 billion in loans and loan guarantees from the Export-Import Bank, a federal agency that underwrites the export of American goods and services, and more than $500 million in grants for work that includes cancer research and the turning of agricultural byproducts into fuel.

In addition, oil and gas companies that have done business in Iran have over the years won lucrative drilling leases for close to 14 million acres of offshore and onshore federal land.

In recent months, a number of companies have decided to pull out of Iran, because of a combination of pressure by the United States and other Western governments, “terrorism free” divestment campaigns by shareholders and the difficulty of doing business with Iran’s government. And several oil and gas companies are holding off on new investment, waiting to see what shape new sanctions may assume.

The Obama administration points to that record, saying that it has successfully pressed allied governments and even reached out directly to corporate officials to dissuade investment in Iran, particularly in the energy industry. In addition, an American effort over many years to persuade banks to leave the country has isolated Iran from much of the international financial system, making it more difficult to do deals there.

“We are very aggressive, using a range of tools,” said Denis McDonough, chief of staff to the National Security Council.

The government can, and does, bar American companies from most types of trade with Iran, under a broad embargo that has been in place since the 1990s. But as The Times’s analysis illustrates, multiple administrations have struggled diplomatically, politically and practically to exert American authority over companies outside the embargo’s reach — foreign companies and the foreign subsidiaries of American ones.

Indeed, of the 74 companies The Times identified as doing business with both the United States government and Iran, 49 continue to do business there with no announced plans to leave.

One of the government’s most powerful tools, at least on paper, to influence the behavior of companies beyond the jurisdiction of the embargo is the Iran Sanctions Act, devised to punish foreign companies that invest more than $20 million in a given year to develop Iran’s oil and gas fields. But in the 14 years since the law was passed, the government has never enforced it, in part for fear of angering America’s allies.

That has given rise to situations like the one involving the South Korean engineering giant Daelim Industrial, which in 2007 won a $700 million contract to upgrade an Iranian oil refinery.

According to the Congressional Research Service, the deal appeared to violate the Iran Sanctions Act, meaning Daelim could have faced a range of punishments, including denial of federal contracts. That is because the law covers not only direct investments, such as the purchase of shares and deals that yield royalties, but also contracts similar to Daelim’s to manage oil and gas development projects.

But in 2009 the United States Army awarded the company a $111 million contract to build housing in a military base in South Korea. Just months later, Daelim, which disputes that its contracts violated the letter of the law, announced a new $600 million deal to help develop the South Pars gas field in Iran.

Now, though, frustration over Iran’s intransigence has spawned a growing, if still piecemeal, movement to more effectively use the power of the government purse to turn companies away from investing there.

Nineteen states — including New York, California and Florida — have rules that bar or discourage their pension funds from investing in companies that do certain types of business in Iran. Congress is considering legislation that would have the federal government follow suit, by mandating that companies that invest in Iran’s energy industry be denied federal contracts. The provision is modeled on an existing law dealing with war-torn Sudan.

Obama administration officials, while indicating that they were open to the idea, called it only one variable in a complex equation. Right now, the president’s priority is on breaking down Chinese resistance to the new United Nations sanctions, which apply across borders and are aimed squarely at entities that support Iran’s nuclear program.



But Representative Ron Klein, a Florida Democrat who wrote the contracting provision moving through Congress with the help of a lobbying group called United Against Nuclear Iran, said it offered a way forward with or without international agreement.

“We need to send a strong message to corporations that we’re not going to continue to allow them to economically enable the Iranian government to continue to do what they have been doing,” Mr. Klein said.

An Unused Tool

Sending a strong message was Congress’s intention when it passed the Iran Sanctions Act in 1996.

The law gives the president a menu of possible punishments he can choose to levy against offending companies. Not only do they risk losing federal contracts, but they can also be prevented from receiving Export-Import Bank loans, obtaining American bank loans over $10 million in a given year, exporting their goods to the United States, purchasing licensed American military technology and, in the case of financial firms, serving as a primary dealer in United States government bonds or as a repository for government funds.

Congress is now considering expanding its purview to a broader array of energy-related activities, including selling gasoline to Iran, which despite its vast oil and gas reserves has antiquated refineries that leave it heavily dependent on imports.

From the beginning, though, the law proved difficult to enforce.

European allies howled that it constituted an improper attempt to apply American law in other countries. Exercising an option to waive the law in the name of national security, the Clinton administration in 1998 declined to penalize the first violator — a consortium led by the French oil company TotalFina, now known as Total.

The administration also indicated that it would waive future penalties against European companies, winning in return tougher European export controls on technology that Iran could convert to military use.

Stuart E. Eizenstat, who as the deputy Treasury secretary handled those negotiations, said the law let Iran “exploit divisions between the U.S. and our European allies.”

Waiving it, though, was followed by additional investments in Iran — and more government largesse for the companies making them.

In 1999, for instance, Royal Dutch Shell signed an $800 million deal to develop two Iranian oil fields. Since then, Shell has won federal contract payments and grants totaling more than $11 billion, mostly for providing fuel to the American military, as well as $200 million in Export-Import loan guarantee and drilling rights to federal lands, records show.

Shell has a second Iranian development deal pending, but officials say they are awaiting the results of a feasibility study. In the meantime, the company continues to receive payments from Iran for its 1999 investment and sells gasoline and lubricants there.

Records show Shell is one of seven companies that challenged the Iran Sanctions Act and received federal benefits.

John R. Bolton, who dealt with Iran as an under secretary of state and United Nations ambassador in the Bush administration, said failing to enforce the law by punishing such companies both sent “a signal to the Iranians that we’re not serious” and undercut Washington’s credibility when it did threaten action.

Mr. Bolton recalled what happened in 2004 when he suggested to the Japanese ambassador that Japan’s state-controlled oil exploration company, Inpex, might be penalized for a $2 billion investment in the Azadegan field in Iran. “The Japanese ambassador said, ‘Well, that’s interesting. How come you’ve never sanctioned a European Union company?’ ” Mr. Bolton recounted.

Inpex was never penalized, though several years later it decided to reduce its stake in the Iranian project. And to Mr. Bolton’s chagrin, the Bush administration did not act on reports about other such investments, neither waiving the law nor penalizing violators.

Recently, after 50 lawmakers from both parties complained to President Obama about the lack of enforcement and sent him a list of companies that apparently violated the law, the State Department announced a preliminary investigation. Officials said that they were looking at 27 deals, and that while some appeared to have been “carefully constructed” to get around the letter of the law, they had identified a number of problematic cases and were focusing on companies still active in Iran.

Competing Interests

Among the companies on the list Congress sent to the State Department is the Brazilian state-controlled energy conglomerate Petrobras, which last year received a $2 billion Export-Import Bank loan to develop an oil reserve off the coast of Rio de Janeiro. The loan offers a case study in the competing interests officials must confront when it comes to the Iran Sanctions Act.

Despite repeated American entreaties, Petrobras had previously invested $100 million to explore Iran’s offshore oil prospects in the Persian Gulf.



But the Export-Import Bank loan could help create American jobs, since Petrobras would use the money to buy goods and services from American companies. Perhaps more important, it could help develop a source of oil outside the Middle East.

After The Times inquired about the loan, bank officials said that they asked for and received a letter of assurance from Petrobras that it had finished its work in Iran. A senior White House official, in a Nov. 13 e-mail message, said that while it was the administration’s policy to warn companies against such investments, “Brazil is an important U.S. trading partner and our discussions with them are ongoing.”

But if the administration hoped that the loan would bring Brazil in line with its objectives in Iran, it would soon prove mistaken.

On Nov. 23, Iran’s president, Mahmoud Ahmadinejad, visited Brazil, and the two countries agreed to share technical expertise on energy projects. Iranian officials said they might offer Petrobras additional incentives for further investment.

The visit infuriated American officials, who felt it undercut efforts to press Iran on its nuclear program while lending international legitimacy to the Iranian president. Brazil’s relationship with Iran has also complicated American maneuvering at the United Nations, where Brazil holds a rotating seat on the Security Council. Just last week, Brazil’s president, Luiz Inácio Lula da Silva, restated his opposition to the administration’s sanctions proposal, warning, “It is not prudent to push Iran against a wall.”

Carter Lawson, the Export-Import Bank’s deputy general counsel, acknowledged that Mr. Ahmadinejad’s visit was “problematic for us, and it raised our antenna.” He said that since December the bank had been operating under a new budget rule requiring borrowers to certify that they had no continuing operations in Iran’s energy industry, and was carefully monitoring Petrobras’s activities.

In the meantime, Petrobras’s Tehran office remains open. And Diogo Almeida, the acting economic attaché at the Brazilian Embassy in Iran, said that while Petrobras was currently assessing how much it could invest in Iran, given the huge discovery off Rio de Janeiro, company officials were in active discussions with the Iranian government and were interested in pursuing new business.

Opportunities for Profit

For all the American rules and focus, there is still plenty of room for companies to profit in crucial areas of Iran’s economy without fear of reprisal or loss of United States government business.

Auto companies doing business in Iran, for instance, received $7.3 billion in federal contracts over the past 10 years. Among them was Mazda, whose cars in Iran are assembled by a company called the Bahman Group. A 45 percent share in Bahman is held by the Sepah Cooperative Foundation, a large investment fund linked to the Revolutionary Guards, according to Iranian news accounts and a 2009 RAND Corporation report prepared for the Defense Department.

A Mazda spokesman declined to comment, saying the company was unaware of the links.

Even companies based in the United States, including some of the biggest federal contractors, can invest in Iran through foreign subsidiaries run independently by non-Americans.

Honeywell, the aviation and aerospace company, has received nearly $13 billion in federal contracts since 2005. That year it acquired Universal Oil Products, whose British subsidiary is working on a project to expand gasoline production at the Arak refinery in Iran. Universal recently received a $25 million federal grant for a clean-energy project in Hawaii.

In a statement, Honeywell said it had told the State Department in January that while it was fulfilling its Arak contract, it would not undertake new projects in Iran.

Ingersoll Rand, another American company with foreign subsidiaries, says it is evaluating its “minor” business in Iran in light of the political climate. But for now, according to a spokesman, Paul Dickard, it continues to sell air-compression systems with a “wide variety of applications,” including in the oil and gas industries and in nuclear power plants.

Senator Byron L. Dorgan, a North Dakota Democrat, tried to close the foreign subsidiary loophole after a furor erupted in 2004 over Halliburton, former Vice President Dick Cheney’s old company, which had used a Cayman Islands subsidiary to sell oil-field services to Iran. But he said he was unable to overcome business opposition.

William A. Reinsch, president of the National Foreign Trade Council, lobbied against Mr. Dorgan’s bill and has opposed other unilateral sanctions. He argues that their futility can be seen in the intransigence of the Iranian government and the way American oil companies have simply been replaced by foreign competitors. Moreover, many foreign companies with business interests in Iran are also large American employers; deny them federal contracts and other benefits, Mr. Reinsch said, “and it’s those workers who will pay the price.”

But Hans Sandberg, senior vice president of Atlas Copco, which is based in Sweden, offered a different perspective. Atlas Copco’s sales of mining and construction equipment to Iran are dwarfed by its American business, including military contracts. If forced to choose, he said: “It would be no problem. We wouldn’t trade with Iran.”