Militants are targeted by drones to keep them from entering Afghanistan.
Bush's orders to send special forces after Taliban militants have roots in previous presidencies.
Asif Ali Zardari leads the race to replace Musharraf in Saturday's presidential election.
US forces may have sent in ground troops for the first time Wednesday. Were they targeting a top Taliban or Al Qaeda figure?
Pakistani military officials fear American intervention in the tribal areas could spark a rebellion, derailing counterterrorism operations.
Aafia Siddiqui, who went missing in Pakistan for five years before her arrest, is accused of trying to kill US Army and FBI officers.