The head of the International Atomic Energy Agency, Mohamed ElBaradei, said today that two months of inspections in Iraq and interviews with Iraqi officials have yielded no evidence to support Bush administration claims that Iraq is secretly trying to revive its nuclear weapons program.

ElBaradei said in an interview that "systematic" inspections of eight facilities linked by U.S. and British authorities to a possible nuclear weapons program have turned up no proof to support the claims. "I think we have ruled out . . . the buildings," he said. ElBaradei also cast doubts on U.S. claims that Iraq has sought to import uranium and high-strength aluminum tubes destined for a nuclear weapons program.

ElBaradei's remarks, combined with a relatively upbeat assessment of Iraq's cooperation with U.N. weapons inspectors, delivered to the U.N. Security Council on Monday, have complicated Bush administration efforts to make a case for military action against Iraq. The remarks also increased pressure on the United States to provide inspection teams with more intelligence regarding Iraq's suspected nuclear weapons program.

The administration's concerns about Iraq's alleged intent to develop nuclear weapons formed the basis of the case President Bush made to the United Nations in September for disarming Iraq. Bush said in an Oct. 7 speech that satellite photographs revealed that "Iraq is rebuilding facilities at sites that have been part of its nuclear program in the past." White House officials produced satellite images showing recent construction at a former uranium enrichment plant at Furat, one of several sites searched by U.N. inspectors.

"At the majority of these sites, the equipment and laboratories have deteriorated to such a degree that the resumption of nuclear activities would require substantial renovation," ElBaradei wrote in his report to the council.

ElBaradei said today that the findings did not prove that Iraq has abandoned its nuclear ambitions. He also faulted Baghdad for failing to provide more "proactive cooperation" that could shed light on Iraq's past weapons programs.

ElBaradei said that continued inspections offered the best chance of deterring Iraq from rebuilding its weapons programs. "We are not getting optimal cooperation," he said. "But still we are inching forward, and we still believe that barring something exceptional, we should be able in a few months to come to a conclusion on Iraq's nuclear weapons program."

Iraq was close to developing nuclear weapons before the 1991 Persian Gulf War. IAEA inspectors said they had destroyed all nuclear facilities and equipment, and removed all weapons material before the inspections ended in 1998.

President Bush raised the specter of a new Iraqi quest for nuclear weapons, telling U.N. delegates during his Sept. 12 address to the U.N. General Assembly that Iraq made "several attempts" to "buy high-strength aluminum tubes used to enrich uranium for a nuclear weapon."

In addition to the U.S. assertion that Iraq had attempted to buy aluminum tubes to enrich uranium, U.S. and British intelligence have claimed that Iraq had tried to purchase low-grade uranium for processing into weapons-grade material from a source in Niger. Despite repeated requests for evidence, ElBaradei said "we haven't gotten anything specific. Niger denied it, Iraq denied it, and we haven't seen any contracts."

ElBaradei said that a preliminary investigation into Iraqi efforts to acquire large quantities of the aluminum tubes between 2000 and 2002 suggested that they were destined for an Iraqi program to build 81mm artillery rockets. He said that further investigation is required to determine whether Iraq may have diverted the tubes to a nuclear weapons program.

"We know that these tubes . . . could be used for conventional rockets," he said. They "cannot be used directly for [uranium] enrichment." ElBaradei said that his inspectors would continue to investigate whether the tubes had been reworked for nuclear weapons use.