U.S. Secretary of State John Kerry is imploring Syria’s warring sides to adhere to the nationwide ceasefire. He says there has been a reduction in violence since the truce began at sundown on Monday. 

He said, “We believe that this is the only possible solution to this conflict is ultimately a political outcome. I urge all the parties to support, because it may be the last chance that one has to save a united Syria.”

Kerry says rebels must stop intermingling with al-Qaida-linked militants. Syria’s government must also allow aid deliveries to besieged areas for the ceasefire to work. The Russian Foreign Ministry says it is counting on the U.S. to use its influence to ensure full compliance to the ceasefire.