US Secretary of State Colin Powell has insisted Iraq did pose a clear danger to America, after a report said its pre-war threat had been exaggerated.
US troops have been searching for WMD in Iraq
The left-leaning Carnegie Endowment for International Peace said US officials misrepresented the threat from Iraqi weapons of mass destruction.
Mr Powell said: "The intelligence community is confident of the material
they gave me."
But he had seen "no smoking gun" that linked Saddam Hussein to al-Qaeda.
The US and UK cited concerns over weapons of mass destruction (WMD) to justify the invasion of Iraq last March.
Mr Powell said he was confident of the presentation he made about Iraq's WMD last year at the United Nations before the war.
"It was information [the intelligence community] presented to the Congress. It was information they had presented publicly and they stand behind it. And this game is still unfolding."
Of Carnegie's finding that Iraq posed no imminent threat,
Mr Powell said: "They did not say it wasn't there."
'No convincing evidence'
The Carnegie Endowment - which opposed the war - also said there was no evidence for the claim that Saddam Hussein would give weapons of mass destruction to terrorists.
It said it had studied hundreds of documents and interviewed dozens of specialists for its report WMD: Evidence and Implications.
The report says there was "no convincing evidence" that Iraq had reconstituted its nuclear programme.
There was greater uncertainty about its biological weapons, it continues, but the threat related to what could be developed in future rather than what Iraq actually had.
The report says it was unlikely Iraq could have destroyed, hidden or moved large amounts of chemical and biological weapons without the United States detecting some sign of activity.
And it adds: "There was no evidence to support the claim that Iraq would have transferred WMD to al-Qaeda and much evidence to counter it."
The study concludes that while the long-term threat from Iraq could not be ignored, it was being contained by a combination of UN weapons inspections, international sanctions and limited US-led military action.
"Administration officials systematically misrepresented the threat from Iraq's WMD and ballistic missile programmes," it contends.
Meanwhile, a 400-strong US team of weapons disposal experts is being withdrawn from Iraq.
US Government officials confirmed reports in the New York Times that the mission was being wrapped up, but stressed that the team had finished its work.
The newspaper reported that 400 - out of a team of 1,400 - had been assigned to search for depots for missile launchers and other equipment that might be used in conjunction with weapons of mass destruction.