US Secretary of State John Kerry said Syria truce was the “last chance to save Syria.”
He told reporters in Washington shortly after the ceasefire came into effect it was “far too early to draw conclusions”.
However, he noted that reports he received two hours after the truce started suggested “some reduction” in violence.
“For all the doubts that remain, and there will be challenges in the days to come, this plan has a chance to work,” he said of the deal he agreed on Friday with his Russian counterpart Sergei Lavrov.
“And I urge all the parties to support it because it may be the last chance that one has to save a united Syria,” Kerry said.
On Friday, Russian Foreign Minister Sergei Lavrov and US Secretary of State John Kerry announced a new plan aimed at reducing violence in Syria, which includes a week-long ceasefire. The two sides said they expected that the truce would evolve into a permanent cessation of hostilities.