The Syrian government has agreed to allow aid convoys into 19 besieged areas this month, UN Syria envoy Staffan de Mistura announced Thursday, calling on the regime to follow through on its promise.
"Of course the proof is in concrete facts, that is, in delivery," de Mistura told reporters in Geneva.
Syrian authorities should not stop convoys at the last moment, should not remove medical supplies from trucks and should not backpedal on the amount of aid that they have authorized, the UN diplomat said, referring to past incidents.
The government approval came as a result of last month's announcement by global and Middle Eastern powers that they would push for air lifts into besieged cities if there were no progress on aid shipments on the ground, de Mistura said.
"The issue of air lifts, air bridges or air drops must remain an option" in case the trucks do not come through, he added.
UN-brokered Syrian peace talks in Geneva have been stalled since May, when opposition delegates suspended their participation to protest lacking aid deliveries and an increase in violence.
"Time is not yet mature for an official third round of intra-Syrian talks," de Mistura said.
However, UN experts was planning to start technical-level talks soon on the future of the Syrian military and civilian institutions after a political transition, he added. These talks would likely be held with the government in Damascus and with the opposition in Riyadh.
While the aid truck approval was a positive development, he said, heavy shelling of the rebel-held Damascus suburb Daraya, and attacks on children's hospitals were "bad news."
Meanwhile, Syrian militia forces were advancing to take control over a main road to Minbij, a key city in the last Islamic State-controlled pocket along the Turkish border, amid heavy fighting and air cover by the US-led coalition.
The Democratic Forces of Syria (DSF), a group dominated by the Kurds but with large Arab contingents, is now laying siege to the city that lies just 20 kilometres from the frontier.
The Minbij Military Council, the largely Arab force leading the attack, said it was holding off on storming the city in order to avoid civilian casualties. There were indications the battle for the city could begin within days.
Turkey, which is wary of the Kurdish forces, has given hesitant backing to the operation against Islamic State but insists the Kurdish People's Protection Units (YPG) cannot remain in the area once the extremist group is ousted.
The mission aims to halt the flow of Islamic State militants across the Turkey-Syria border, kick them off the frontier and take over their supply routes to al-Raqqa, the group's de-facto capital.
A separate DSF operation was launched last month to take northern al-Raqqa. The Syrian government is moving on the city from the west.
Defence ministers from Russia, Syria and Iran are set to meet in Tehran to discuss strengthening collaboration against Islamic State and al-Qaeda's Syrian wing known as al-Nusra Front.