well ... Nec ... regarding US attacking Pakistan is quite possible, US supported Afghanistan through pakistan's president in 1980's in war against Soviet Union and the support was taken back as soon as there was no Soviet Union on world's map but only Russia and soon after that our president Zia was also killed in a plane crash! what happened to saddam? Saddam was totally supported by US but when there interests were gone, he was executed! This is US policy they always do this! why Iraq was invaded ... OIL!!!! do you think there is any other reason? I dont! It has always come to "OUR NATIONAL INTERESTS" as qouted by almost all presidents of US!!!

but on the other hand it is not so easy for US to attack pakistan ... due to its strategic location! our borders touch three big countries ... India China and Russia!!! except for india the other two are not "friends" with US so they will have to be careful in doing so ...

and about China's support to pakistan ... i would add only one thing ... china has its own "logical" interests ... they cannot afford presence of US in pakistan!