The Bush administration has confirmed that a 400-strong team of weapons disposal experts was withdrawn from Iraq but insists their job was done.
The search goes on for conventional arms and WMD
President Bush's spokesman also stressed that the hunt for weapons of mass destruction continues.
News of the pullout came as a prominent think-tank accused the US Government of exaggerating the Iraqi threat.
The US and UK cited concerns over weapons of mass destruction to justify the invasion of Iraq last March.
News that the Joint Captured Materiel Exploitation Group had been withdrawn was leaked to the New York Times before being confirmed by the Bush administration.
Their work was done, officials quoted by the newspapers said.
"They picked up everything that was worth picking up," one official said.
However, a senior Pentagon official denied suggestions that the team had been quietly withdrawn, saying the last members left Iraq in October as previously planned.
They were there to search for a broad scope of conventional weapons, as well as weapons of mass destruction, including helicopters and missile launchers, the official said, and their mission was completed.
The Bush administration is also stressing that the larger Iraq Survey group, which is the team looking specifically for weapons of mass destruction, is still in business.
"The Iraq Survey Group continues to do its work," White House spokesman Scott McClellan told reporters.
The experts' withdrawal has, however, given further ammunition to critics of the Bush administration, the BBC's Justin Webb in Washington says.
That criticism has also been fuelled by a report by the influential left-of-centre Carnegie Endowment for International Peace, which opposed the war in Iraq.
The think tank said the weapons inspections process was working before the war and the Bush administration had "systematically exaggerated" the Iraqi threat.
The Carnegie Endowment also says that the Bush administration should re-think its flagship doctrine of pre-emptive military action against emerging threats.
Asked about the report, US Secretary of State Colin Powell insisted that Iraq had dangerous weapons and needed to be disarmed.
He defended the case he made to the UN Security Council last year in which he accused Iraq of possessing weapons of mass destruction.
"I am confident of what I presented last year, the intelligence community is confident of the material they gave me," Mr Powell told reporters.