The Bush administration still maintains there could be Weapons of Mass Destruction (WMD) in Iraq despite their chief investigator quitting.
Mr David Kay stepped down saying he did not believe the country had any large stockpiles of chemical or biological weapons.
Doubts about Saddam's supposed weapons programmes were underlined by the Mr Kay's resignation which followed eight months heading up the Iraq Survey Group's search for WMD.
His comments increased the pressure on President George Bush and on British Prime Minister Tony Blair, who is bracing himself for Wednesday's publication of the potentially explosive Hutton report into the death of government weapons expert Dr David Kelly.
Mr Blair today faced a chorus of demands to admit he committed British forces to the Iraq war on the basis of a flawed intelligence.
Former foreign secretary Mr Robin Cook challenged Mr Blair on BBC radio today to admit the war was a mistake when he addresses the Commons after Hutton is published.
In the US, the White House is standing firm. "We remain confident that the Iraq Survey Group will uncover the truth about Saddam Hussein's regime [and is] weapons of destruction programmes," spokesman Mr Scott McClellan said.
Mr Kay's replacement, former UN weapons inspector Mr Charles Duelfer - who has expressed his own doubts that unconventional weapons would be found - said today: "My goal is to find out what happened on the ground. What was the status of the Iraqi weapons programme? What was their game plan? What were the goals of the regime? To find out what is the ground truth."