The Syrian opposition warned on Sunday that attacks by the army, backed by Russian warplanes, threatened a U.S.-Russian deal for a cessation of hostilities with collapse and endangered future peace talks. The agreement, which is in its second day and has drastically curbed violence but not stopped it entirely, is the first of its kind to be attempted in four years. In a letter to U.N. Secretary-General Ban Ki-moon, the opposition said violations would undermine international efforts to guarantee the continuation of the truce and lead to the collapse of the UN-adopted political process. The Riyadh-based opposition body said Russian war planes on Sunday staged 26 bombing raids on areas where rebel groups abiding by the truce were operating and accused Moscow of deploying cluster bombs on residential areas it […]