** Rebel fighters execute civilians in Damascus ** Approximately 170 Syrians were killed Saturday ** U.S. Steps Up Aid to Syrian Opposition, Pledging $60 Million ** Obama and Putin seek 'new Syria initiatives' ** John Kerry holds talks on Syria crisis in Ankara ** Syrian army, rebel clashes bring conflict to Iraq doorstep ** U.N. Warns of Dire Rise in Refugees From Syria ** Syria, Iran say Assad to remain in power till 2014 ** Kerry in Cairo to discuss Syria **