Iran repeatedly misstated details about its nuclear program and pursued uranium enrichment technology more aggressively than it initially admitted, the International Atomic Energy Agency concluded yesterday in a sharply critical assessment.
The report by the United Nations' nuclear watchdog raises new questions about Iran's intentions and appears certain to persuade the agency's board of governors not to end intrusive inspections when it meets later this month.
The 20-page document is the third consecutive quarterly report to raise significant doubts about Iran's performance. It comes as the Bush administration, which has pledged to prevent Iran from developing nuclear weapons, struggles to curb a proven atomic weapons program in North Korea.
The IAEA credited Iran with providing fresh information about its nuclear efforts, but cited a wide array of missing details and contradictory explanations in a confidential report to board members obtained yesterday.
After declaring that it had built all of its uranium enrichment equipment, for example, Iran recently admitted to IAEA inspectors that essential magnets were imported from Asia.
Questioned further on the basis of new IAEA information, Iranian officials also admitted that an Iranian company had contacted a European intermediary about buying 4,000 magnets for sophisticated P-2 gas centrifuges -- enough for 2,000 machines, more than needed for simple research.
Indeed, Iran made such fast progress in assembling and testing advanced P-2 centrifuge equipment that IAEA experts expressed doubts about Iranian assertions that the project lay dormant for six years after scientists first acquired designs in 1995.
The IAEA also raised fresh doubts about Iran's assertion that uranium enriched to 36 percent U-235 had come from used centrifuge parts imported from Pakistan via Abdul Qadeer Khan's illicit supply network. The amounts the agency found on those parts were larger than the traces one would find from prior use, the agency said.
One possibility, officials said yesterday, is that quantities of enriched uranium are available on the international market, possibly originating in Russia.
IAEA investigators trying to identify the source of enriched uranium traces in three Iranian facilities could not follow the trail mapped by the Iranian authorities.
"Their explanation was so complex that it was not particularly helpful in helping the agency figure out the origin," said a diplomat in Vienna, who spoke on condition of anonymity. "The origin is going to be very important."
Iran has been slow to reveal information about the centrifuge project and other matters, the IAEA report said. Understanding the program "frequently required repeated requests, and in some cases continues to involve changing or contradictory information."
The IAEA assessment comes amid signs that European governments that tried to negotiate a suspension of Iran's nuclear program last year are frustrated with Tehran's response. Iran counters that the Europeans have not fulfilled promises of economic and diplomatic cooperation.
The document provides support for Bush administration officials who contend that Iran is hiding an atomic weapons program behind an insistence that the goal is nuclear energy.
"It's absolutely full of unanswered questions and things that don't compute," said a U.S. official, who requested anonymity. "It's a strong argument for the need to continue the investigation."
The IAEA report is a quarterly update on Iran's compliance with an international safeguards pact. A November report revealed the existence of a secret 18-year-old nuclear project, and a February review faulted Iran for hiding the extent of its program despite promises to reveal details.
Much of the report's focus is on previous Iranian statements and contradictory new information produced by Iran voluntarily or under pressure. Iran, for example, changed its account of what happened to several pounds of uranium hexafluoride, saying first that it had leaked, then affirming that it had been used in research.
In another case, the Iranian government told U.N. inspectors that rotors for gas centrifuges were manufactured by a private company in Tehran when, in fact, they were built at an Iranian defense industry site, the IAEA said.
The agency checked to see whether Iran had halted enrichment-related activities and suspended the manufacture, assembly and testing of centrifuges, as the Tehran government promised the IAEA in February.
Inspectors found that Iran continued to assemble rotors for P-1 centrifuges until April. Between February and April, the U.N. report said, Iran assembled 285 rotors.