The coalition force massing in the Persian Gulf so far consists of two US Marine divisions, three US Army divisions and one British division. France has alerted forces, probably a brigade or two, for service in the Gulf. Meanwhile, secret defection negotiations go on with Iraqi military officers and government officials. During the 1991 war, the US force consisted of  eight US divisions (including three armored divisions), two US Marine divisions, a British division, a French division and four Arab divisions. In addition there were 5,000 Special Forces troops and over 2,000 warplanes.  

It's a long shot, but the invasion could be called off if Iraq's ruling party removed Saddam from power and radically changed it's domestic and foreign policy. Such a move could get interesting, as there would be a call to have Saddam turned over for a war crimes trial.