In an interview with an Australian radio station broadcast Wednesday, Blix said it was unlikely that the U.S and British teams now searching for weapons in Iraq would find more than some "documents of interest."
"I'm certainly more and more to the conclusion that Iraq has, as they maintained, destroyed all, almost, of what they had in the summer of 1991," Blix told Australian Broadcasting Corp. radio.
"The more time that has passed, the more I think it's unlikely that anything will be found."
Blix indicated he thought the U.S.-led coalition had backtracked on the issue of Iraq's weapons.
"In the beginning they talked about weapons concretely, and later on they talked about weapons programs. Maybe they'll find some documents of interest," he said.
The administration has also focused more frequently on Iraq's older weapons programs. Secretary of State Colin Powell on Monday honored 5,000 Iraqi Kurds who died in a chemical weapons attack blamed on Iraq.
Blix, who spent three years searching for Iraqi chemical, biological and ballistic missiles as head of the U.N. Monitoring, Verification and Inspection Commission, said Iraq might have tried to fool the United States into believing it had weapons of mass destruction over the years in order to deter attack.
"I mean, you can put up a sign on your door, 'Beware of the Dog,' without having a dog," he said from his home in Sweden.
The United States and its allies Britain and Australia invaded Iraq in May after saying Saddam Hussein's regime was developing nuclear arms as well as chemical and biological weapons.
However, a search by the U.S.-led Iraq Survey Group — which is made up of some 1,400 scientists, military and intelligence experts — has yet to report finding any weapons of mass destruction since the conflict ended.
President Bush and British Prime Minister Tony Blair have come under increasing pressure to prove that Iraq had weapons of mass destruction. Blair has faced two parliamentary probes, both of which cleared him of deliberately exaggerating Iraq's threat but faulting the way he described it.
A separate inquiry into the suicide of a top British weapons expert has uncovered doubts among intelligence officers on the way the case for war was made.
In the United States, the CIA says two trailers discovered in northern Iraq may have been biological weapons factories, but State Department analysts disagree. The White House has withdrawn the claim that Iraq sought uranium in Niger.
An interim report on the search for Iraqi weapons is due soon, but there are indications the reports findings might be inconclusive.
In July, David Kay, the survey group's leader, suggested that he had seen enough evidence to convince himself that Saddam Hussein had had a program to produce weapons of mass destruction. He expected to find "strong" evidence of missile delivery systems and "probably" evidence of biological weapons.
But last week, Defense Secretary Donald Rumsfeld said he had met with Kay, and that the onetime weapons inspector had not informed him of any finds.
The Times of London reported this weekend that the report had been postponed because of lack of evidence. But CBS News has learned there is no delay.
Last week, in a confidential report obtained by The Associated Press, the International Atomic Energy Agency chief said U.N. inspectors found Iraq's nuclear program in disarray and unlikely to be able to support an active effort to build weapons.
Former weapons inspectors now say, five months after the U.S. invasion, that what the U.S. alleged were "unaccountable" stockpiles may have been no more than paperwork glitches left behind when Iraq destroyed banned chemical and biological weapons years ago.
Over the weekend, Vice President Dick Cheney insisted that evidence will be found to back up the administration's claims.