T-butt:

In July 2002, the 23d, the Prime Minister of England attended a meeting of high level British government wonks, among whom was the British Defence Secretary.

The minutes of that meeting included the following:

C reported on his recent talks in Washington. There was a perceptible shift in attitude. Military action was now seen as inevitable. Bush wanted to remove Saddam, through military action, justified by the conjunction of terrorism and WMD. But the intelligence and facts were being fixed around the policy. The NSC had no patience with the UN route, and no enthusiasm for publishing material on the Iraqi regime's record. There was little discussion in Washington of the aftermath after military action.

The rest of that memo can be found here.

While this does not pre-date September 11th, it certainly predates any of the publicized panics about Saddam's WMD.

A