For all the negotiating at the UN, I suspect the decision as to the necessity of such action was made a long time ago and that the White House is depending on Saddam’s gift for miscalculation to provide the catalyst for an invasion.The opinion polls suggest that a substantial number of people have doubts about attacking Iraq, but that was the case too before the last Gulf War, in fact before any significant American military action in the last 20 years. Once war gets under way the polls tend to shoot up and stay that way – as long as the war is short and there aren’t too many American boys coming home in body bags. The massive loss of life in the attacks on America may have changed public willingness to accept military casualties, but this remains to be tested.For Tony Blair, it has been a fortunate week. Had the last frantic round of negotiations at the UN not delivered a compromise everybody could live with, Mr Blair could have been forced to back an American military attack against the protests of many in his party and a large part of public opinion.

There may yet be a moment of crisis within the party if Saddam frustrates the inspectors and triggers a conflict, but the UN resolution will make it harder for Mr Blair’s opponents to drum up a broad protest against military action.So the devil is not in the detail of the resolution. Forget the verbal circumlocution of the last week, the Americans have got what they wanted from the outset. The nations who have signed the resolution know that it paves the way for war if Saddam refuses to disarm. Some of them may believe a war is inevitable, others will hope that Iraq will endure the humiliation of disarmament and get everybody off the hook.The problems arise from the unpredictable character of the Iraqi regime and the nature of war itself. Saddam Hussein could look at this resolution, ponder the length of time it took to get agreement and decide that he will risk frustrating the inspections. The council might have backed the resolution, but would all its members really support an invasion of Iraq?The international consensus on Iraq is fragile and could shatter if civilian casualties were large.

Neither can Mr Bush be certain his domestic support would hold up if the war turned into a bloodbath. He might have finally to answer the difficult question: what has this to do with fighting al-Qa’ida? The White House believes that the war would be won swiftly and with minimum loss of life. If that calculation is wrong, then the triumph of the mid-term elections and the UN diplomacy could be quickly replaced by bitterness and recrimination.Of course, now that President Bush has won such overwhelming backing at home and abroad, the moment of crisis may never come. In seven days we will get the first hint of how Iraq plans to deal with this ultimatum. Saddam may break the habit of a lifetime and admit defeat, complying “promptly and unconditionally”, as President Bush has demanded I wouldn’t bet on it The writer is a BBC Special Correspondent.