A U.S.-Russian brokered ceasefire for southwest Syria has come into force today. The announcement came after a meeting between U.S. President Donald Trump and Russian President Vladimir Putin at the G20 summit in Germany.<br/><br/>The Syrian Observatory for Human Rights, a Britain-based war monitoring group, said calm was prevailing with no air strikes or clashes in the southwest since the truce began at noon. <br/><br/>The United States, Russia and Jordan reached a ceasefire and de-escalation agreement this week with the aim of paving the way for a broader, more robust truce.<br/><br/>Several ceasefires have crumbled since the onset of the conflict and it was not initially clear how much the combatants, Syrian government forces and the main rebels in the southwest, were committed to this latest effort.