By Jonathan Marcus
BBC defence correspondent
The US Defence Secretary, Donald Rumsfeld, has acknowledged for the first time that Iraq may have destroyed its weapons of mass destruction before the US launched its offensive to topple Saddam Hussein's regime.
So is the Bush administration backing away from its insistence that Iraq did indeed have weapons of mass destruction on the eve of the war?
The US has conceded Iraq may have destroyed its arms
The public justification for the British and American decision to go to war to oust Saddam Hussein was the clear and imminent threat said to have been posed by his regime's weapons of mass destruction.
The Bush administration, followed by the British Government, seized upon significant failures by Iraq to account for its weapon programmes to UN inspectors as a clear indication that Saddam Hussein had something to hide.
This was backed up countless intelligence briefings about active weapons programmes.
Just wait - was the underlying message - all will be revealed once British and US troops are actually on the ground in Iraq and the regime has been toppled.
But several weeks on, the whole question of Iraq's weapons programmes remains shrouded in mystery.
Searches have failed to find any prohibited weapons
There have been few spectacular finds.
Documents have been found. At least two trailers have been discovered which could be mobile biological weapons production facilities.
But the search for Saddam Hussein's weapons appears to have been haphazard at best.
While the Americans and British have insisted that significant resources are being deployed in the hunt, the fact remains that many sensitive sites - including Iraqi nuclear facilities - may well have been looted and potential evidence destroyed.
Mr Rumsfeld insists that more information will come to light as Iraqi leaders and maybe hundreds of scientists and technicians are interviewed.
But even he now is forced to admit that Iraq may have destroyed much of its chemical and biological arsenal prior to the war.
The Bush administration and the war's supporters will say "So what?
Iraq retained the know-how and probably also the desire to have such weapons again in the future."
But this was not the basis on which the case for this conflict was made.
Regime change in Iraq was said to be a necessary condition for disarmament, not an end in itself.