In northern Syria, a US-supported Kurdish-Arab alliance today pressed its advance towards the town of Manbij held by the Islamic State jihadist group.
A US-led coalition is backing offensives against the extremists in Syria and neighbouring Iraq where forces have surrounded the IS-held city of Fallujah.
Humanitarian access in Syria has been a key sticking point in stalled UN-backed peace talks aimed at ending the five-year war that has killed at least 280,000 people and displaced millions.
Calls from London and Paris for aerial aid came despite supply deliveries yesterday to two towns besieged by government forces where civilians are facing food shortages.
A local truce allowed a convoy to enter the town of Daraya near Damascus for the first time since late 2012, while another entered the nearby town of Moadamiyeh for the first time since March.
But Syria's opposition said only medical supplies were in the Daraya delivery and British charity Save the Children said it was "shocking and completely unacceptable" that it excluded desperately needed food.
Britain has called for an emergency Security Council meeting tomorrow to discuss humanitarian access and to press ahead with air drops.
"It's too little, too late," said British envoy Matthew Rycroft, referring to yesterday's land deliveries.
French ambassador Francois Delattre, who holds the council presidency this month, blamed the Syrian regime for blocking access to towns and villages under siege.
"France is asking the United Nations and in particular the WFP to begin humanitarian air drops for all the areas in need, beginning with Daraya, Moadamiyeh and Madaya, where the civilian population including children risks dying of hunger," Delattre told a press conference.
It however remains unclear whether the Syrian government will give its approval for air drops.