Pakistani troops have killed 16 Taliban militants after coming under attack in a volatile tribal region on the Afghan border.More than 60 militants reportedly stormed a post of paramilitary Frontier Corps in a predawn attack in the Spin Tangi area of Mohmand and killed two soldiers. It is the fifth consecutive day of clashes in the area bordering Afghanistan’s eastern province of Kunar as security forces battle to take control of the strategic Buner valley. The creeping advances by militants are causing growing alarm in the United States about the stability of its nuclear-armed ally. Pakistan is vital for the U.S. efforts to defeat al Qaeda and Taliban and restore order in Afghanistan. US officials say calls for increased US training of Pakistani troops will likely be discussed when Pakistani President Asif Ali Zardari visits Washington next week.