They are reluctant about us kicking Saddams ass out of Bagdad... so they help initiate (or at least do nothing to stop) a diversion....
Strategically if Iraq is out of the way the US's power can be focused right on Asia, not to mention the influence on China's oil supplies...
Not that we are going to steal Iraqs oil feilds or anything...but a moderate non anti US Bagdad would be a pain in the ass for China in the long term.
Funny how the visit was only 4 days ago.