Chief U.N. inspector Hans Blix (search) criticized the United States for insisting so vehemently that Iraq has weapons of mass destruction (searchand not producing the evidence.

The failure of U.S.-led teams to find illegal weapons after more than two months of searching and visits to over 230 suspected sites has become a major issue. Saddam Hussein's possession of banned weapons was the main justification the United States and Britain used for invading Iraq.

"It is sort of puzzling I think that you can have 100 percent certainty about the weapons of mass destruction's existence, and zero certainty about where they are," he said. "We were more prudent in our assessment and I think that was shown to be pretty wise."

Blix, who is retiring when his contract ends on June 30, spent an hour fielding questions Monday at the Council on Foreign Relations (searchand defending his conclusion that there is still no evidence that Saddam was hiding weapons of mass destruction.

He questioned the Bush administration's rush to declare that two mobile vans discovered by U.S. search teams after the war were "the smoking gun" -- used to produce biological weapons.

"Only later came the various doubts from both the U.S. experts and from the British experts," Blix said. "I would have thought that ... after the shakiness of some of the evidence that one would be very prudent."

He said the United States was not alone in believing that Iraq had weapons of mass destruction. "I think all the Western intelligence agencies that I met were fairly convinced that there were weapons of mass destruction," he said, though Russia never "came out affirmatively."

Blix said U.S. teams may yet find banned weapons, but the more time goes by, the more the question arises of whether Saddam's regime destroyed its weapons programs in 1991 -- as it claimed.

The question would then arise of why Iraq played cat and mouse with U.N. inspectors for so many years.

He raised three possibilities: Saddam wanted to create a mystique in the region that he had weapons; he had tremendous pride and saw himself as "the emperor of Mesapotamia;" and he was engaging in brinkmanship, listening to the anti-war demonstrators and not believing the United States would "dare to do it."

With U.N. inspection teams barred from returning to Iraq by the United States, Blix was more critical of the "shaky" intelligence he received from Washington and other capitals about sites where weapons might be hidden.

He reiterated that U.N. inspectors "were not impressed" by some of the evidence presented to the Security Council by Secretary of State Colin Powell -- and he was particularly dismissive of intelligence from Iraqi defectors, saying they "have not been a reliable source."

U.N. inspectors were only allowed to search for 3 months before the United States and Britain launched their invasion, which Blix said was too short.