By CHARLIE SAVAGE and MARK LANDLER
WASHINGTON


President Obama has vowed to keep the pressure on Iran over its nuclear program after this month’s meeting in Geneva, and his advisers said the United States was intensively recruiting other nations to join in a harsher economic embargo against Tehran should diplomacy fail.

But as the focus on sanctions intensifies, a review of the United States’ experiences in enforcing its own longstanding restrictions on trade with Iran suggests it would be difficult to quarantine the Iranian economy.

Black market networks have sprouted up all over the globe to circumvent the sanctions. A typical embargo-busting scheme was detailed in a plea agreement filed in federal court here on September 24, the day before Mr. Obama and European allies announced the existence of a previously undisclosed Iranian nuclear enrichment facility near Qum.

In the court filings, a Dutch aviation services company and its owner admitted that they had illegally funneled American aircraft and electronics components to Iran from 2005 to 2007. Under the scheme, Iranian customers secretly placed orders with the company, which served as a front, buying the parts and having them shipped to the Netherlands, Cyprus and the United Arab Emirates. The materials were then quietly repackaged and shipped on to the real buyers in Iran.

The Dutch company was eventually caught. But the ease with which it had operated until then illustrates a key hurdle facing the United States: even if diplomatic challenges can be overcome to persuade countries with significant economic ties to Iran, like China, to approve sanctions, it is virtually impossible to make an embargo airtight.

“The Iranians have a lot of experience at this point in evading sanctions,” said Michael Jacobson, an intelligence and sanctions specialist at the Washington Institute for Near East Policy. “They are adaptable, learn from mistakes, see where the United States cracks down and move elsewhere. And on the part of businesses, there is a lot of willful blindness.”

On October 1, Iranian officials met in Geneva with representatives from the United States and other world powers. At that session, the Iranians pledged to give nuclear inspectors access to its clandestine enrichment facility and to ship most of its openly declared uranium outside the country to be further enriched by France or Russia.

While viewed as progress, the meeting drew further attention among diplomats to the role of possible new sanctions. To hold Iran to its pledges, and to prevent it from dragging its feet on the larger objections to its nuclear program, officials said Iran would need to feel a credible threat of punitive measures.

“If you don’t put yourself in a position where you can act on the pressure track, you’ll be less likely to have the engagement track work,” said a highranking administration official, who spoke on the condition of anonymity because of the delicacy of the matter. “The key is for the Iranians to see both sides of this.”

The United States is refusing to take any measures off the table, even an embargo of gasoline and other fuel. European countries fear such measures would inflict misery on the Iranian people, and drive them into the arms of an unpopular government.

Existing sanctions have had some practical consequences. In Tehran, the power goes out regularly, a result of a shortage of electricity generators, which are on the list of prohibited goods because of their potential for military use. That did not happen a decade ago.

Still, the experience of the United States in policing its own unilateral economic sanctions - which were imposed after the 1979 hostage crisis and expanded several times since then - shows that restrictions are more likely to drive up prices of banned foreign goods than to stop them from flowing into Iran. The world is full of rogue nations and smugglers, and other nations may not be as willing as the United States to police sanctions rigorously.

The guilty plea by the Dutch avionics company late last month was just the latest in a string of indictments against several hundred such defendants since 2007, when the Bush administration significantly increased efforts to enforce the United States’ own trade restrictions with nations like Iran.

In cases over the past few months alone, prosecutors have accused defendants of illegally routing fighter jet parts to Iran through Colombia, electronic components through Malaysia and helicopter parts through Singapore. Accused intermediaries have been in places including Ireland and Hong Kong.

Financial sanctions have also been violated. In January, the London bank Lloyds TSB agreed to pay $350 million in fines for hiding the involvement of entities in countries including Iran on wire transfers with United States banks over a 12-year period. In 2006, regulators fined the Dutch bank ABN Amro for similar sanctions-busting dealings from 1997 to 2004.

Mr. Jacobson said that even strict sanctions, enforced with broad international support, would be unlikely to seal off a country as large and complex as Iran.

“While it’s unrealistic to expect that you can isolate Iran from the international economy,” he said, “the narrower and more realistic goal of raising their cost of doing business may change their leaders’ calculations.”


THE NEW YORK TIMES