Pakistan warned U.S. troops not to intrude on its territory Friday, after the two anti-terror allies traded fire along the volatile border with Afghanistan. Thursday’s five-minute clash adds to already heightened tensions at a time the United States is stepping up cross-border operations in a region known as a haven for Taliban and al-Qaida militants. The clash — the first serious exchange with Pakistani forces acknowledged by the U.S. — follows a string of other alleged border incidents and incursions that have angered many here.
