US Defense Secretary Donald Rumsfeld said today he believed it was "just a matter of time" before evidence of weapons of mass destruction were found in Iraq, and that it was still early in the hunt.
"I have reason, every reason, to believe that the intelligence that we were operating off was correct and that we will, in fact, find weapons or evidence of weapons, programs, that are conclusive. But that's just a matter of time," he told a Pentagon media briefing.
Critics have raised questions about whether top US and British officials exaggerated the threat from Iraq's banned weapons programs to make a stronger case for war.
US forces have not found any biological or chemical weapons in Iraq, and some Democratic presidential candidates have raised the WMD issue to criticise the current Republican administration.
"It's now less than eight weeks since the end of major combat in Iraq and I believe that patience will prove to be a virtue," Mr Rumsfeld said.
He said no one had contended that Iraq had nuclear weapons, but Baghdad had admitted in the 1990s that it had biological and chemical warfare agents and had not accounted for what happened to them.
Some congressional Democrats say that at a time when the administration has a policy of pre-emptive strikes against those deemed a threat, it is essential that the evidence be solid.
They are calling for a full-blown investigation into whether the threat from Iraq's banned weapons had been exaggerated to gather support for the war.
"If we are going to hit first, based on perceived dangers, the perceptions had better be accurate," Sen. Robert Byrd, a West Virginia Democrat, said on the Senate floor.
"Whether or not intelligence reports were bent, stretched, or massaged to make Iraq look like an imminent threat to the United States, it is clear that the administration's rhetoric played upon the well-founded fear of the American public about future acts of terrorism," he said.