British Foreign Secretary Jack Straw says military action against Iraq is "now much more probable".
He insists that neither US President George W Bush nor the Prime Minister, Mr Tony Blair, who are holding an emergency summit in the Azores tomorrow, have taken the decision to go ahead with an attack.
But he said: "The prospect of military action is now much more probable and I greatly regret that." But, he told the BBC, a conflict with Iraq "is not inevitable."
There is still time for Saddam Hussein to disarm, he added.
But the Foreign Secretary's remarks are the clearest signal yet by the British government that war is imminent.
"What we are seeking to do still is to pursue this by diplomatic means," he said.
"What we know about Saddam Hussein from all his behaviour is that he only responds to pressure and only responds at the last minute. So there is still time for him to comply but time is running out."
Underlining Britain's hardline stance against Iraq, Mr Straw said Saddam had been "in the most flagrant breach of the United Nations".
"He was given this final opportunity in resolution 1441, and the overwhelming evidence is that he has failed to take it.
"If we don't follow through what 1441 also made clear which was that if he failed to take the final opportunity then serious consequences would have to happen, then it's then that the authority of the UN is called into question."
PA