Syrian rebels see flaws in U.S.-Russian truce plan

By Arshad Mohammed and Tom Perry WASHINGTON/BEIRUT (Reuters) - The United States and Russia announced plans for a 'cessation of hostilities' in Syria that would take effect on Saturday but exclude groups such as Islamic State and al Qaeda's Nusra Front, a loophole that Syrian rebels immediately highlighted as a problem. Monday's agreement, described by a U.N. spokesman as "a first step towards a more durable ceasefire", is the fruit of intensive diplomacy between Washington and Moscow, which bac