TUZLA, Bosnia-Herzegovina: U.S. troops will take on a new task in Bosnia this week as peacekeepers will provide security for U.N. war crimes investigators. NATO's commander in Bosnia does not expect any major confrontations during the search for mass graves and other atrocities near Srebrenica, in eastern Bosnia. 'There may be some demonstrations," Adm. Leighton Smith said. "This obviously is a very emotional issue. But I don't anticipate that there will be problems" for the American troops. The investigators will begin examining graves on Tuesday for planned excavation. Reports that thousands of Bosnian Muslims were slaughtered by Bosnian Serbs near Srebrenica helped trigger NATO's peacekeeping mission. TIME's Massimo Calabresi says that while this week's action is mostly exploratory, the involvement of U.S. troops is significant. "People who have criticized the IFOR mission will certainly applaud whatever role U.S. troops undertake in guarding the war crime tribunal investigators." While this may be a first step in U.S. involvement in arresting indicted war criminals, Calabresi says any arrests are still a long way off. "It is significantly more complicated to launch an arrest operation than to provide security," Calabresi says. "In the past, IFOR has said it is unwilling to engage in those types of operations. That is the type of operation that caused trouble in Somalia, so people are nervous about undertaking them here."