It is more than two months since the Syrian government agreed to what was called a "cessation of hostilities" - effectively a ceasefire brokered by Russia and the US.
Though it was shaky from the start, US Secretary of State John Kerry says it has had a "profoundly positive effect" and saved many lives.
But any progress seems to have been shattered over the past 11 days or so.
Syrian regime air strikes and artillery attacks on rebel-held areas of Aleppo have killed hundreds of people.
The rebels are also accused of targeting civilians and attacking a hospital.
Now UN envoy Staffan de Mistura is trying to salvage what is left of the truce by pressuring Russia and the US.
Can diplomatic efforts to restore a nationwide ceasefire work?
Presenter: Hazem Sika
Jean-Marc Rickli - Assistant professor at the Department of Defence Studies at King's College London.
Samir al Taqi - General Director of the Orient Research Centre, Dubai.
Vladimir Sotnikov - Strategic analyst in the Institute of Oriental Studies at the Russian Academy of Sciences.
Source: Al Jazeera