Pakistans army has sent home two-thirds of the U.S. military personnel who were training its forces in counterinsurgency skills along the porous border with Afghanistan. A senior Pakistan military official said late Tuesday that 90 of an estimated 135 U.S. trainers have left the country, the latest setback in the deeply troubled relationship between the United States and Pakistans military following the May 2 U.S. raid that killed al-Qaida leader Osama bin laden. The 90 Americans had been training the Frontier Corps, a paramilitary force made up mostly of tribesmen from the frontier areas, according to the military official, who asked not to be named in accordance with military practice. The Frontier Corps is Pakistans front line force against militants in the tribal regions. The U.S. military personnel were teaching members of the force to become trainers. The U.S. has confirmed it is reducing the number of its military personnel in Pakistan but has not given an exact figure.