I agree with Bobby. The Administration desire to re-invade Iraq is well documented and predates the events of 9/11. See the book by Bob Woodward, "Bush at War", where Adminstration motives and tactics are laid out. (Woodward is a fan of Bush, generally.) The attack Iraq policy was pushed by Vice President Dick Cheney, Deputy Secretary of Defense Paul Wolfowitz, and former defense advisory board chairman Richard Pearl (no doubt there are many others.) The WMD excuse and the much hinted-at 9/11 Iraq connection were just part of the sales package to the public. Wolfowitz recently let the cat out of the bag as reported in the Eurpoean press coverage of a conference held in Singapore:

From The Guardian, 6/4/03.

Asked why a nuclear power such as North Korea was being treated differently from Iraq, where hardly any weapons of mass destruction had been found, the deputy defence minister (sic)said: "Let's look at it simply. The most important difference between North Korea and Iraq is that economically, we just had no choice in Iraq. The country swims on a sea of oil."