VIENNA -- The U.N. nuclear agency on Thursday said it was worried Iran may currently be working on making a nuclear warhead, suggesting for the first time that Tehran had either resumed such work or never stopped at the time U.S. intelligence thought it did.
The report by the International Atomic Energy Agency appeared to put the U.N. nuclear monitor on the side of Germany, France, Britain and Israel. These nations and other U.S. allies have disputed the conclusions of a U.S. intelligence assessment published three years ago that said Tehran appeared to have suspended such work in 2003.
The U.S. assessment itself may be revised and is being looked at again by American intelligence agencies. While U.S. officials continue to say the 2007 conclusion was valid at the time, they have not ruled out the possibility that Tehran resumed such work some time after that.
Iran denies any interest in developing nuclear arms. But the confidential report, made available to The Associated Press, said Iran's resistance to agency attempts to probe for signs of a nuclear cover-up "give rise to concerns about possible military dimensions to Iran's nuclear program."
Ali Asghar Soltanieh, Iran's envoy to the IAEA, told the official IRNA news agency that the report "verified the peaceful, nonmilitary nature of Iran's nuclear activities."
But in Washington, U.S. State Department spokesman P.J. Crowley said the findings were consistent with what Secretary of State Hillary Rodham Clinton has been saying "on our ongoing concerns about Iran's activities."
The language of the report -- the first written by Yukiya Amano, who became IAEA head in December -- appeared to be more directly critical of Iran's refusal to cooperate with the IAEA than most of those compiled by his predecessor, Mohamed ElBaradei.
It strongly suggested that intelligence supplied by the U.S., Israel and other IAEA member states on Iran's attempts to use the cover of a civilian nuclear program to move toward a weapons program was compelling.
"The information available to the agency ... is broadly consistent and credible in terms of the technical detail, the timeframe in which the activities were conducted and the people and organizations involved," said the report, prepared for next month's IAEA board meeting.
"Altogether, this raises concerns about the possible existence in Iran of past or current undisclosed activities related to the development of a nuclear payload for a missile," said the report, which was also sent to the U.N. Security Council.
Iran is weathering three sets of Security Council sanctions meant to punish its refusal to freeze its uranium enrichment program. It's recent rejection of a plan meant to strip it of most of its enriched stockpile plus its belated acknowledgment that it had been secretly building a new enrichment facility has increased sentiment for a fourth set.
The U.S., Britain and France support such a measure, with Russia undecided and fellow permanent Security Council member China -- which depends an Iran for much of its energy needs -- opposed.
Listing suspect activities known to it, the agency said it sought information on high-precision detonator and other explosives experiments; studies on setting off explosions high in the atmosphere; "whether the engineering design and computer modeling studies aimed at producing a new design for the payload chamber of a missile were for a nuclear payload," and other nuclear activities with a possible military link.
"Addressing these issues is important for clarifying the agency's concerns about these activities ... which seem to have continued beyond 2004," said the report.
The allegations build on material provided to the IAEA by U.S. intelligence from a laptop computer that reportedly was smuggled out of Iran. In 2005, U.S. intelligence assessed that information as indicating that Tehran had been working on details of nuclear weapons, including missile trajectories and ideal altitudes for exploding warheads.
Thursday's 10-page IAEA report did not go into specifics, and it many of the alleged activities listed had appeared in previous reports. But a senior international official familiar with the IAEA probe of Iran said the agency continued to receive new intelligence from agency member nations on activities allegedly linked to attempts to build nuclear arms.
Among the newer pieces of information being weighed by the agency and U.S. intelligence agencies is the significance of a technical document, which appears to describe a work plan for developing a neutron initiator, used to detonate a nuclear bomb.
A government official recently told the AP that document had been known to American intelligence for more than a year and had already been factored into current analysis of Iran's nuclear program.
The report also confirmed Iranian claims of being able to enrich uranium to near 20 percent.
The senior official said the amount enriched to 19.8 percent in two days of operation last week was minute. Still, it was an important development that moved Tehran closer to the ability to make weapons grade uranium, should it opt to do so.
While enriching Iran's present stockpile of low enriched uranium to 20 percent would take about one year, using up to 2,000 centrifuges at Tehran's underground Natanz facility, any next step -- moving from 20 to 90 percent -- would take only half a year and between 500-1,000 centrifuges.
Iran has already amassed about 2 tons of low-enriched uranium -- more than enough for further enrichment into material for one warhead. An IAEA-endorsed plan foresees taking 70 percent of that material to Russia for 20-percent enrichment and then to France for processing into fuel rods for Tehran's research reactor.
The proposal was endorsed by world powers because it would ensure a continued supply of medical isotopes from the reactor for Iranian cancer patients while at the same time delaying Iran's ability to further enrich to weapons grade uranium by stripping it of most of its low-enriched stockpile.
But the Islamic Republic rejected the plan and said it would make the reactor fuel on its own -- a technical feat that world powers assert Iran is incapable of.
Associated Press writers Barry Schweid in Washington and Nasser Karimi in Tehran contributed to this report.