FILE - In this Feb. 22, 2012 file photo, Afghan security guards stand at the scene as the remnants of a tire burn during an anti-U.S. demonstration in Kabul, Afghanistan. Two U.S. troops were gunned down by two Afghan soldiers and an accomplice Thursday, March 1, 2012, the latest of six American service members killed by their Afghan partners since the burning of Muslim holy books at a U.S. base last week sent anti-Americanism soaring in a nation that has long distrusted foreigners. (AP Photo/Ahmad Jamshid, File)