Air drops of vital aid to besieged areas of Syria are "not imminent", a senior UN official has warned.
But Ramzi Essedine Ramzi, UN deputy special envoy for Syria, said the "process that will lead to air drops has already started".
He was speaking after the US, UK and France urged the UN to deliver by air.
They say the Syrian government has failed to respect a 1 June deadline for widespread aid distribution agreed by world and regional powers.
A convoy of aid reached besieged Darayya suburb of the capital Damascus on Wednesday, but it carried only a small amount of medicines and other non-food items. Darayya has been without food aid since 2012.
UN humanitarian coordinator Jan Egeland said a convoy of food for Darayya, planned for Friday, may be delayed but added there are "clear indications" it will go ahead within days.
The UN Security Council is expected to meet on Friday to discuss the question of air drops, foreign media reports.