Prime Minister Tony Blair is to urge MPs to back his approach over Iraq in a speech to the Commons on Tuesday ahead of a full debate on the crisis on Wednesday.
Tony Blair must persuade MPs to support him
This is turning into the most extraordinary political cliffhanger we have had for a very long time.
Certainly Tuesday will the most important speech that Tony Blair has given in the House of Commons during his premiership.
The rebellion is serious and spreading there.
Since 1997 we have become accustomed to talk about the House of Commons as if it did not matter so much.
It was no longer the "cockpit of the nation" or any of those similarly romantic phrases.
But now it matters enormously to Tony Blair and the future politics of the UN in a way it has not mattered before.
He is going to have to confront MPs with the strange paradox which is that the best chance of avoiding war is persuading Saddam Hussein that he has absolutely no chance to do anything except disarm.
But what may persuade him to carry on playing games is the peace party in the west - the divided Europeans, the marchers on the streets of London and the divided Labour party.
He must convince MPs that it is those people who are sending out the message that will persuade Saddam Hussein that he can carry on playing games and not disarm and this in turn will therefore make an attack within weeks inevitable.
That is a difficult argument but, nevertheless, he has to get it across.
A motion in the Commons on Monday that said that the case for war had not been made attracted at least 80 signatures compared with 44 or so a month ago.
So there is no doubt that the sense of unease about war is far from receding but rather is spreading.
This is a dynamic and exceedingly dangerous situation for the prime minister.