Seymour Hersh is the best source the US has.
If you don't believe Hersh, you are a fool, plain and simple.
If you don't believe W would start WWIII, open the gates of hell and invite the meltdown of the human race, you are not paying attention.
This really sums it up. (And as far as I can tell this story still has not shown up on the CNN website. I keep looking. If anybody has seen it, please let me know. I'd love to be wrong.)