The CIA and other Western spy services have provided sensitive information to the Vienna-based International Atomic Energy Agency since 2002, but none of the tips about supposed secret weapons sites provided clear evidence that the Islamic Republic is developing illicit weapons.

"Since 2002, pretty much all the intelligence that's come to us has proved to be wrong," a senior diplomat working at the IAEA was quoted as saying by The Los Angeles Times.

Another official here described the agency's intelligence stream as "very cold now (because) so little panned out." The reliability of US information and assessments on Iran is increasingly at issue as the Bush administration confronts the emerging regional power on multiple fronts: its expanding nuclear effort, its alleged support for insurgents inside Iraq and its backing of Middle East militant groups.

The CIA faced harsh criticism for its pre-war intelligence errors on Iraq.

IAEA officials, who openly challenged US assessments that Saddam Hussein was developing a nuclear bomb, say the Americans are much more cautious in assessing Iran.

American officials privately acknowledge that much of their evidence on Iran's nuclear plans and programs remains ambiguous, fragmented and difficult to prove, the report said.