European leaders on Thursday called on Syria and Russia to ensure the safety of civilians being evacuated from Aleppo amid charges that the West had failed to protect them.
At a summit in Brussels marked by one of the most turbulent years in EU history, the bloc's 28 leaders are also grappling with Brexit, the migration crisis and sanctions against Moscow over the war in Ukraine.
The leaders opened their meeting by hearing from the mayor of eastern Aleppo, who warned of thousands more casualties if Europe failed to press for the protection of civilians.
"The 50,000 citizens of eastern Aleppo are only waiting for their deaths after the failure of the international community," Brita Hagi Hassan said.
French President Francois Hollande accused Russia of "making commitments that it is not keeping" urged Moscow and Tehran to "take the responsibility for this extremely serious situation."
But Francois Fillon, the favourite to succeed Hollande in next year's elections, said the fall of Aleppo marked the failure of western foreign policy.
Fillon -- in Brussels for meetings on the sidelines of the summit -- also hinted at talks with Assad, saying the West should be ready to deal with all parties in Syria, "even those today committing crimes."
British Prime Minister Theresa May meanwhile said the bloc "must also do all we can to ensure a ceasefire is secured so that the United Nations can help bring to safety the innocent people of Aleppo."
The 28-nation summit is drafting a statement condemning Syria and Russia, amid debate on whether to officially call on them to give the UN access to civilians in eastern Aleppo, European officials said.
But they will stop short of warning of sanctions against Russia, opting as they did at the last summit in October to say that "the EU is considering all available options," according to a draft seen by AFP.
Sanctions against Russia imposed in 2014 over the conflict in eastern Ukraine are however due to be extended, in another crisis that sees the West at loggerheads with Moscow, officials said.
Later, the summit will turn to Brexit with May being frozen out of a dinner for the other 27 EU leaders at which they will try to present a united front over how they handle Britain's departure.
They have rejected all negotiations until Britain officially triggers the two-year divorce process, expected in March, but May dismissed any suggestion that it amounted to a snub.
"It is right that the other leaders prepare for those negotiations as we have been preparing," she said.
The British government separately rejected a report Thursday that its ambassador to the EU had warned that it could take up to ten years to agree a new trade deal after Brexit.
"This is the ambassador reflecting the views of others which have been put to him," May's spokesman said.
May also met with outgoing European Parliament chief Martin Schulz and the leaders of Lithuania and Latvia.
Germany's Schulz earlier kicked off an EU turf war, warning that MEPs could block any deal if it is not involved in negotiations, which are currently set to be led by the European Commission.
The one-day summit, cut back from the usual two days, wraps up an 'annus horribilis' for the bloc that has seen it face a wave of eurosceptic populism including the shock Brexit referendum vote in June.
The thorniest issue on Thursday could be Dutch Prime Minister Mark Rutte's efforts to negotiate a way past a referendum in April in which his country voted against a key EU-Ukraine pact.
The Netherlands is the only EU state that has not ratified the deal so far.
Rutte wants to lock in a vow that the pact is not a first step towards EU membership for Ukraine, and that it will not provide defence guarantees to Kiev.
"Taking the agreement off the table would be the biggest present ever we could give to (Russian President) Vladimir Putin," Rutte warned.
The West is however carefully considering its next steps with Moscow, particularly as it eyes US President-elect Donald Trump's apparent closeness to Putin.