Agencies Suspect Iran Is Planning Atomic Sites

The United Nations inspectors assigned to monitor Iran’s nuclear program are now searching for evidence of two such sites, prompted by recent comments by a top Iranian official that drew little attention in the West, and are looking into a mystery about the whereabouts of recently manufactured uranium enrichment equipment.

In an interview with the Iranian Student News Agency, the official, Ali Akbar Salehi, head of Iran’s Atomic Energy Organization, said President Mahmoud Ahmadinejad had ordered work to begin soon on two new plants. The plants, he said, “will be built inside mountains,” presumably to protect them from attacks.

“God willing,” Mr. Salehi was quoted as saying, “we may start the construction of two new enrichment sites” in the Iranian new year, which began March 21.

The revelation that inspectors from the International Atomic Energy Agency, the United Nations’ nuclear watchdog, now believe that there may be two new sites comes at a crucial moment in the White House’s attempts to impose tough new sanctions against Iran.

When President Obama publicly revealed the evidence of the hidden site at Qum last September, his aides had hoped the announcement would make it easier to win international support for a fourth round of economic sanctions, particularly from a reluctant China and Russia. Since then, however, the White House has been struggling to persuade those countries to go along with the toughest sanctions and the administration is now being forced to scale back its proposed list of sanctions.

The United Nations inspectors operate separately from the diplomats who are developing sanctions. Still, the disclosures may be intended, at least in part, to underscore the belief of Western officials that the Iranian efforts are speeding ahead, and the assertions could aid in efforts to press Iran to open up locations long closed to inspectors.

This article was based on interviews with officials of several governments and international agencies deeply involved in the hunt for additional nuclear sites in Iran, and familiar with the work of the I.A.E.A., the only organization with regular access to Iran’s known nuclear facilities. All the officials insisted on anonymity because the search involves not only satellite surveillance, but also intelligence gleaned from highly classified operations.

American officials say they share the I.A.E.A.’s suspicions and are examining satellite evidence about a number of suspected sites. But they have found no solid clues yet that Iran intends to use them to produce nuclear fuel, and they are less certain about the number of sites Iran may be planning.

In any case, no new processing site would pose an immediate threat or change the American estimates that it will still take Iran one to four years to obtain the capability to build a nuclear weapon. Given the complexity of building and opening new plants, it would probably take several years for the country to enrich uranium at any of the new sites.

One European official noted that “while we have some evidence,” Iran’s heavy restrictions on where inspectors can travel and the existence of numerous tunneling projects were making the detection of any new enrichment plants especially difficult.

Iran boasted several months ago, after the disclosure of the Qum site, that it would build 10 more enrichment plants in coming years. That number was dismissed by American officials and others as a fantasy, far beyond Iran’s abilities, or its budget.

But I.A.E.A. inspectors in Vienna now believe that Mr. Salehi was probably accurate when he referred to two sites.

According to American officials, in recent weeks Israel — which uncovered some of the evidence about Qum — has pressed the case with their American counterparts that evidence points to what one senior administration official called “Qum look-alikes.”

The most compelling circumstantial evidence, people familiar with the inspectors’ view say, is that while Iran appears to be making new equipment to enrich uranium, that equipment is not showing up in the main plant that inspectors visit regularly. Nor is it at the Natanz site in the desert, or the new facility at Qum, which inspectors now visit periodically.

That has heightened suspicions that the equipment, produced in small factories around Iran, is being held in a clandestine storage area for later shipment or installed elsewhere.