"The situation in East Ghouta — a town in the outskirts of Damascus — poses a potential threat to the ceasefire and upcoming talks in Geneva," de Mistura said following talks with French Foreign Minister Jean-Marc Ayrault in Paris.
The envoy expressed hope that the Syrian opposition would be able to form delegations to Geneva talks so that he would not have to interfere in the process.
De Mistura added that the UN mediators had repeatedly asked Russia and Turkey to maintain control over the situation in East Ghouta.
The UN-brokered inter-Syrian negotiations are scheduled to resume on February 20 in Geneva.
The first round of the intra-Syrian peace talks, which was held in Astana, the capital of Kazakhstan, on January 23-24, resulted in an agreement between Russia, Turkey and Iran on establishing trilateral mechanism to monitor the ceasefire regime in Syria.