Vienna, Austria ? The U.N. atomic agency is coming under fire for saying it has no evidence that Tehran tried to make nuclear weapons.

In a report detailing two decades of covert Iranian nuclear activity, the agency said Iran was guilty of numerous secret experiments, including uranium enrichment and the production of small amounts of plutonium that effectively put the nation in violation of the Nuclear Nonproliferation Treaty.

But the document, presented this week to the International Atomic Energy Agency’s board of governors, also praised Tehran for cooperation and openness. It said the agency had found “no evidence” of an Iranian nuclear weapons program. That stance contradicts the American view that Tehran is not only trying to make such arms but could be just years away from putting nuclear warheads on missiles capable of reaching Israel.

In Washington, Undersecretary of State John R. Bolton said Wednesday the agency’s finding was “simply impossible to believe.” But in Iran officials say it should dispel suspicions their country had a nuclear weapons agenda.

“This proves our claim and removes the possibility for some powers to misuse the situation against us,” Iranian President Mohammad Khatami said.

The board will be looking closely at the report, written by agency Director General Mohamed ElBaradei, when it meets Nov. 20. Any finding that Iran violated the nuclear treaty brings with it Security Council involvement.

The Security Council can impose sanctions as its ultimate weapon. At the least, it could be asked to note concerns about Iran’s nuclear program but take no action while the agency continues to probe the country’s activities.

The Bush administration wants the agency’s board to take a strong and unified stance, but there is concern now that it may not even refer the matter to the Security Council.