"If Russia is concerned about civilians in eastern Ghouta, it should halt its planes immediately from bombing towns and residences and should stop the regime of Assad from its war of extermination", Alloush said.
In tandem with the military operations in Eastern Ghouta, the army is securing the humanitarian corridor between the Wafidin area and Eastern Ghouta to allow civilians to leave toward government-run shelters.
On Thursday, 24 civilians were killed in air strikes and rocket fire on Eastern Ghouta, the Britain-based Syrian Observatory for Human Rights monitor said.
Defeat in eastern Ghouta would mark the worst setback for the rebels since the opposition was driven from eastern Aleppo in late 2016 after a similar campaign of siege, bombing and ground assaults.
Security concerns and other "developments on the ground" led to the convoy being postponed, Sedky said, adding that she could not comment on specific developments.
Almost 950 civilians have been killed since Russia-backed government forces launched a blistering assault on the last opposition bastion near Damascus on February 18.
On Monday, a convoy carrying much-needed food and medical supplies entered the rebel enclave for the first time since the Syrian government launched a deadly offensive on the area two weeks ago.
UN renews calls for cease-fire in Syria as concerns over humanitarian crisis escalate
The same NGO said that since the escalation of raids started on February 18, at least 867 civilians have been killed, including 186 minors.
"Daily, we hear of an increasing sense of hopelessness and despair, as our medical colleagues reach the limits of what a person can be expected to do", MSF director-general Meinie Nicolai said.
Rescue workers and opposition activists in eastern Ghouta meanwhile have accused the government of using chlorine gas during the campaign. The trucks had been stuck at the Wafideen crossing the entire week, waiting to enter to deliver the remaining food parcels and flour bags.
The military gains have caused large-scale internal displacement as civilians flee government advances toward areas in the territory still held by the rebels. "Convoys need to come in with food and supplies, and the last convoy was only half unloaded", said Fore.
A top United Nations aid official is appealing to Russian Federation and the Syrian government and those who have influence over armed opposition groups for a cessation of hostilities in eastern Ghouta.
Ambulances and green buses - usually used to evacuate people from areas retaken by the regime - waited near a key checkpoint out of the enclave, an AFP reporter there said, as national songs blared on loudspeakers.
State television reported on Friday morning that the army had control over the village of Beit Sawa, where rebel officials on Thursday said insurgents had recaptured some positions.