"You can say some of the tribes are harboring Al Qaida, but not the national government."
Well then, "some of the tribes" meet Bush's criteria stated 9/20/2001 for being our enemy, for harboring terrorists.
It should make no difference if the form of government is nation-state, or ancient tribal control.
In terms of international law, they are within Pakistan's borders, and therefore is accountable and responsible for their harboring activities.
Why not use greater pressure on Pakistan to act? Do we just let Pakistan off the hook, with the excuse they cannot do anything?
You need to learn more about Pakistan. We will not nor should not do anything which could lead to the fall of that government and give control of its nukes to the terrorists.
Mushareff has been a good ally and must operate with the knowledge that many of his country men are anti-US. This requires a delicate balancing act which constrains our freedom of action.