The admission came after an article in "The Washington Post" yesterday reported that Charles Duelfer, the top U.S. weapons inspector, ended his work in late December 2004.
In September 2004, Duelfer submitted a draft report to the U.S. Congress, saying deposed Iraqi leader Saddam Hussein had the intent -- but not the capacity -- to make weapons of mass destruction.
The report will be completed in the coming weeks.
White House spokesman Scott McClellan said yesterday that the report's findings are not expected to change. But he said the decision by President George W. Bush to invade Iraq was still justified.
"Based on what we know today, the president would have taken the same action, because this is about protecting the American people," McClellan said.
In excerpts from a U.S. television interview due to be broadcast tomorrow, Bush himself defends the decision, saying the removal of Hussein has made the world a safer place.
But the end of the weapons search eliminates one of Washington's key reasons for the war in Iraq -- a campaign that has cost the lives of more than 1,350 U.S. troops, 150 coalition soldiers, and thousands of Iraqi civilians.
Guillaume Parmentier is the director of the French Center on the United States at the French Institute of International Relations. He says that, from a European perspective, the White House admission comes as no surprise.
"I think the effect is behind us, because the fact that the Americans are now admitting that they will never find these weapons doesn't change the situation, which is that the Americans went to war on a pretext that was proven to be wrong. And I would say that everyone in the rest of the world believed this to be the case for a very long time," Parmentier says.
Parmentier notes there was a general belief, even in Europe, that Iraq had maintained small holdings of biological agents like anthrax and smallpox. But such reserves, it was thought, were not enough to substantiate Bush's charge that Iraq was gathering weapons with the intent of launching an attack on the United States.
The evaporation of the original White House justification for the war comes as a number of countries -- notably Poland and Ukraine -- are taking steps to withdraw their troops from Iraq.
Parmentier says the pullouts may have little military impact but may still prove embarrassing for the United States.
"The last thing that Iraq needs now is more foreign troops. And in fact the best thing is probably that there would be fewer troops, because they serve as a rallying cause for the insurgents. What needs to be done urgently is extensive training of Iraqi forces, which, of course, is not an easy thing and will take a little time. But that is the key, and the presence of foreign troops is not essential. From a political standpoint, it is certainly bad that a country like Ukraine is withdrawing its troops just as it is becoming a democracy. That is obviously not a very good sign for the Americans," Parmentier says.
Other U.S. allies are feeling the heat, as well.
British Prime Minister Tony Blair -- who is increasing the number of U.K. troops in Iraq by 400 -- has been criticized for using faulty intelligence in making his case for war.
And opposition politicians in Australia called today for Prime Minister John Howard to admit his country joined the Iraq invasion on false pretenses.