The advance on Mudeira, after the capture of the neighbouring town of Misraba on Saturday, has driven a wedge deep inside rebel territory, leaving the major towns of Douma and Harasta cut off. "I'm afraid that the more than 5,500 families are facing a potential genocide", added Hassoun.
The agreement would offer safe passage to rebels and civilians who wanted to leave and the town would come under government control.
"This is a debate we will have in the coming hours at the United Nations, where it will be shown that the concessions on the ground from Russian Federation, but first and foremost the Syrian regime and its Iranian allies, are insufficient", Macron said.
A day earlier, the Syrian army split Eastern Ghouta into three parts after advancing in the battles there, tightening the siege on Douma in the north, the city of Harasta in the west and other towns and villages south of Eastern Ghouta. The cellars were already packed before that.
The town's opposition-controlled authorities said on Monday the situation there had become "catastrophic", with no more room below ground for civilians to hide.
"We urge all parties in the southwest de-escalation zone not to take actions that would jeopardize the ceasefire and make future cooperation more hard".
According to Hassoun, the situation in Harasta is becoming increasingly hard as hundreds of families are facing one of two options: remaining in their homes and underground refuges as air strikes target them or handing themselves over to government forces.
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He said that he was disturbed by reports of civilian casualties from bombings by regime head Bashar Assad's forces. The number of victims injured or dead are unknown.
"We also warn any nation that is determined to impose its will through chemical attacks and inhuman suffering, most especially the outlaw Syrian regime, the United States remains prepared to act if we must", Haley said.
The Observatory confirmed talks were taking place on Hammuriyeh, as well as the towns of Kafr Batna, Jisreen and Saqba, but said no agreement had yet been reached.
Syrian jets struck rebel-held towns in the country's south on Monday, the first aerial attacks on the area since the United States and Russian Federation reached an agreement making it a "de-escalation zone" previous year, rebels and residents said.
Rebel groups in eastern Ghouta have vowed they will fight on.
Syrian regime forces advanced against rebels in Eastern Ghouta and pounded two towns with air strikes on Monday (Mar 12), as they moved closer to retaking the opposition enclave on the edge of Damascus.
At least 353,935 people have died since, including more than 106,000 civilians, the Observatory said on Monday, providing a new overall death toll for the conflict.