United States Defence Secretary Donald Rumsfeld suggested on Tuesday that the participation of America's closest ally, Britain, in the combat phase of disarming Iraq was in doubt.
'Until we know what the UN resolution is going to say, we won't know the answer as to what their role will be,' Mr Rumsfeld said of the British military, which is deploying 45,000 troops to the Gulf.
'And to the extent they are able to participate -- in the event the president decides to use force -- that would obviously be welcomed,' he added. 'To the extent they're not, there are workarounds and they would not be involved, at least in that phase of it.'
Asked whether that meant the US was considering going to war without Britain, Mr Rumsfeld said 'that is an issue the president will be addressing in the days ahead, one would assume'.
British Prime Minister Tony Blair faces enormous public opposition to his stance in support of President George W Bush.
In London, government officials were reportedly surprised at Mr Rumsfeld's comments.
Mr Blair's office told The Associated Press: 'This does not change anything. We are still working for a second resolution. We are not at a state of military combat but there has been complete cooperation between the Britain and the United States throughout on the military planning side.'
Mr Rumsfeld spoke as the US Air Force tested its biggest non-nuclear bomb, dropping a 9,450 kg bomb onto a test range in Florida. Officials wouldn't say whether more were on hand for use in Iraq, but they hoped the test would rattle Iraqi soldiers bracing for war.