US Secretary of State John Kerry vowed on Monday to extend the truce to the city of Aleppo where violence continues to rise, sabotaging peace talks.
Kerry said Syria's civil war is "in many ways out of control" and that he will talk with his Russian counterpart Sergei Lavrov to push for the ceasefire to extend to Aleppo.
Violence in Aleppo threatens to break the peace talks, which are set to start again at an uncertain date, after breaking up in April when the opposition delegation walked out.
"We're getting closer to a place of understanding, but we have some work to do, and that's why we're here," Kerry said during his meeting with Saudi Arabia's Foreign Minister Adel al Jubeir..
In and around Aleppo, a week of fighting has killed more than 250 people.
Kerry said that Assad regime deliberately targeted three clinics and a hospital, where doctors and patients were.
"The attack on this hospital is unconscionable," he said. "And it has to stop."
The Syrian war has caused hundreds of thousand of deaths, driven millions of people to flee their country, creating the world's biggest refugee crisis.
The fighting has drawn in global powers and regional states, while all diplomatic efforts to resolve it have foundered over the fate of Syrian regime leader Bashar al Assad, who refuses to accept opposition demands that he leave power.
The extreme violence has killed many civilians while many people refuse to leave. About 350,000-400,000 people are believed to exist in rebel-held areas which was once populated by 2 million people.