World powers including Russia and the United States have agreed to plans to air-drop food and other supplies to towns besieged by the Assad regime in Syria, in a key test of the ceasefire.
The air drops will start on June 1, if the regime continues to obstruct land access to more than a dozen towns across the country in desperate need of support.
The agreement, which follows months of pressure from Syrian support groups, aid groups and British MPs, came out of talks between the major international backers of all sides in the conflict intended to pave the way for a resumption of peace negotiations in Geneva.
Little progress has been made in setting the terms of a peace deal, with the western nations backing the opposition in saying they expect President Bashar al-Assad to stand down, while Russia stands by the regime.
No new date for fresh negotiations was announced.
But the various countries of the so-called "International Syrian Support Group" said they wanted to extend the ceasefire which has operated on and off since February, with penalties for those who broke it.
This could mean exclusion from the ceasefire altogether.
The ISSG also renewed its push for humanitarian aid to be delivered to besieged towns and cities, a key condition set by the opposition for it to take part in peace talks and in theory set in stone by a United Nations security council resolution in December. Nevertheless, aid convoys have repeatedly been refused permission to travel through blockades by the regime.
Last week, one such convoy containing baby milk was turned back from the town of Daraya - the regime had insisted only medical supplies, not food, was on board.
Staffan de Mistura, the UN envoy on Syria, said that the ISSG had insisted on "concrete steps" now being taken.
"Starting June 1, if the UN is denied humanitarian access to any of the designated besieged areas, the ISSG calls on the World Food Programme to immediately carry out a programme for air bridges and air drops for all areas in need," he said.