I don't believe that's the issue. They're going to get caught when the war goes down, regardless. Their only hope of getting away with it was to come discreetly clean to the U.S., and give us full support on the war effort. In exchange, all the French fingerprints would magically "go away". No harm, no foul.
There must be some other game afoot.
They gambled that they could prevent the removal of Saddam, and thus not have to come clean at all. They lost, and by the time it was clear that they had lost it was too late for that.