The U.N. nuclear agency said it is "increasingly concerned" about a stream of intelligence suggesting that Iran continues to work secretly on developing a nuclear payload for a missile and other components of a nuclear weapons program.
In its report, the International Atomic Energy Agency said "many member states" are providing evidence for that assessment, describing the information it is receiving as credible, "extensive and comprehensive."
The restricted 9-page report was made available Friday, shortly after being shared internally with the 35 IAEA member nations and the U.N. Security Council. It also said Tehran has fulfilled a pledged made earlier this year and started installing equipment to enrich uranium at a new location — an underground bunker that is better protected from air attack than its present enrichment facilities.
Iran's envoy to the IAEA, Ali Asghar Soltanieh, dismissed what he called "baseless allegations" about Iran's program.
But he nevertheless described the report as a step in the right direction, saying it showed that Iran had fully cooperated with the IAEA by allowing a senior nuclear inspector full access to atomic sites during a five-day visit last month.
"This new trend of positive cooperation between Iran and the IAEA should continue," Soltanieh told Reuters.
The report also strengthened suspicions that — like Iran — North Korea turned to black market suppliers to set up its uranium enrichment plant. The report says the layout of equipment and other details observed last year by a visiting U.S. group were "broadly consistent" with designs sold by a "clandestine supply network."
The report seems to allude to the black market suppliers led by Pakistani scientist A.Q. Khan. That group provided Iran with the backbone of what was a clandestine nuclear program before it was revealed eight years ago.
In Iran's case, enrichment can produce both nuclear fuel and fissile warhead material, and Tehran — which says it wants only to produce fuel with the technology — is under four sets of U.N. Security Council sanctions for refusing to freeze enrichment, which it says it needs for fuel only.
It also denies secretly experimenting with a nuclear weapons program and has blocked a four-year attempt by the IAEA to follow up on intelligence that it secretly designed blueprints linked to a nuclear payload on a missile, experimented with exploding a nuclear charge, and conducted work on other components of a weapons program.
In a 2007 estimate, the U.S. intelligence community said that while Iran had worked on a weapons program such activities appeared to have ceased in 2003. But diplomats say a later intelligence summary avoided such specifics, and recent IAEA reports on the topic have expressed growing unease that such activities may be continuing.
The phrase "increasingly concerned" has not appeared in previous reports discussing Iran's alleged nuclear weapons work and reflects the frustration felt by IAEA chief Yukiya Amano over the lack of progress in his investigations.
His report said that choice of language is due to the "possible existence in Iran of past or current undisclosed nuclear related activities" linked to weapons work. In particular, said the report, the agency continues to receive new information about "activities related to the development of a nuclear payload for a missile."
Acquired from "many" member states, the information possessed by the IAEA is "extensive and comprehensive ... (and) broadly consistent and credible," said the report.
Other findings of the report, prepared for a session of the IAEA's 35-nation board of governors starting Sept. 12 included:
— Confirmation of reports by diplomats to the AP that Iran has started setting up uranium enriching centrifuges at Fordow, a fortified facility dug into a mountain near the holy city of Qom. Iran intends to use Fordow to triple its 20-percent enrichment of uranium — a concern because that level is easier to turn into weapons grade uranium quickly than its main stockpile of low enriched uranium at 3.5 percent.
— Further accumulation of both low-enriched and higher enriched or 20 percent uranium. The report said Iran had now accumulated more than four tons of low enriched uranium and over 70 kilograms — more than 150 pounds — of higher enriched material. Those two stockpiles give it enough enriched uranium to make up to six nuclear warheads, should it choose to do so.
The report praised Iran for its decision earlier this month to allow IAEA Deputy Director General Herman Nackaerts to tour a facility where it is developing more efficient centrifuges, saying Iran "provided extensive information" on its development of such machines.
It, however was generally critical of Iran's record of secrecy and lack of cooperation, noting that without increased openness on the part of the Islamic Republic the IAEA is unable to "conclude that all nuclear material in Iran is in peaceful activities."
The Associated Press and Reuters contributed to this report.