The Iraqi government wouldn't answer a lot of questions about its chemical and biological weapons, the UN's chief inspector said on Thursday. But for Hans Blix, that's not evidence that Iraq has stockpiles of illegal weapons.

"There is a long list of items unaccounted for, but it is not justified to jump to the conclusion that something exists, just because it is unaccounted for," Blix said.

The 40-page report delivered on Thursday was Blix's last. He's to retire at the end of June.

He has called on the Security Council to allow UN inspectors to resume the search for Iraq's proscribed weapons that was halted in early March, just before the U.S.-led invasion.

Now that Saddam Hussein's regime is gone, Blix said, "it should be possible to establish the truth we all want to know."

The unaccounted-for weapons could have been either destroyed or hidden by the Iraqis, Blix said.

Blix didn't mention the U.S. opposition to a resumption of UN arms inspections, but the failure of U.S. forces to find any weapons of mass destruction in 11 weeks of searching 230 sites has become a hot political issue in Washington, London and elsewhere.

Both the British and U.S. governments have been coming under increasing fire over allegations they fudged the intelligence reports they used to justify the war.

Speaking to troops in Qatar on Thursday, U.S. President George W. Bush vowed to find the truth about Saddam's weapons, claiming that some had already been found.

But he referred to tractor-trailers that he said were biological weapons labs – claims that the Pentagon and U.S. weapons hunters have already backed away from.