Ukraine crisis: Leaders upbeat after Moscow talks
The leaders of Russia, France and Germany have held "constructive and substantive" talks on ending the conflict in Ukraine, diplomats say.
Russian President Vladimir Putin, France's Francois Hollande and German Chancellor Angela Merkel met for more than four hours in Moscow.
Mr Hollande and Mrs Merkel had brought with them a peace proposal details on which have not been released.
Russia is accused of arming pro-Russian separatists - a claim it denies.
The Kremlin also rejects claims by Ukraine and the West that its regular troops are fighting alongside the rebels in the eastern Donetsk and Luhansk regions.
Clashes have left nearly 5,400 people dead since April, the UN says.
A September ceasefire, signed in Minsk in Belarus, has failed to stop the violence. Since then the rebels have seized more ground, raising alarm in Kiev and among Ukraine's backers.
Analysis: Bridget Kendall, BBC News, Moscow
There was no joint press conference or statement from the Russian, German and French leaders after such a high-profile Kremlin meeting. Chancellor Merkel and President Hollande left for the airport straight away. But if there was no breakthrough, there was also no breakdown.
Comments from officials from all three countries had clearly been co-ordinated. In Moscow, Paris and Berlin they all described the talks as substantive and constructive. They all noted that the three leaders, plus the president of Ukraine, would confer again by phone on Sunday.
And they all said work would continue on a possible blueprint for a deal, based on the French and German initiative, with added proposals from President Poroshenko and President Putin.
The fact that few details have been made public is probably positive. It suggests this is an attempt to negotiate seriously, without rhetoric and out of the public eye. But it also means we do not really know what is on the table, how far apart the various parties are and how fragile this latest mission to bring peace to Ukraine might be.
The peace proposal Mr Hollande and Mrs Merkel took to Moscow on Friday was crafted with the Ukrainian government on Thursday.
Russia's Dmitry Peskov said after Friday's talks that work was continuing on a joint document. Further talks will be held by phone on Sunday, he added.
Earlier, Mr Hollande said the aim was not just a ceasefire but a "comprehensive agreement" - although Mrs Merkel said it was "totally open" whether that could be achieved.
Major questions any plan would have to address include the route of any new ceasefire line - given the rebel advances of recent weeks - how to enforce it, and the future status of the conflict zone, says the BBC's Sarah Rainsford in Moscow.
Moscow is still denying any direct role in the conflict, while Kiev insists above all that Ukraine must remain united, our correspondent says.
Meanwhile US Vice-President Joe Biden accused Russia of "continuing to escalate the conflict" and "ignoring every agreement".
He was speaking in Brussels, where he is meeting top EU officials.
He accused Mr Putin of continuing "to call for new peace plans as his tanks roll through the Ukrainian countryside".
He said Russia could "not be allowed to redraw the map of Europe".
Washington is considering Ukrainian pleas for better weaponry to fend off the rebels, raising European fears of an escalation in the conflict and spurring the latest peace bid.
Also on Friday, a truce allowed civilians to leave Debaltseve in Donetsk region - a town at the heart of an upsurge in fighting in recent weeks.
On Friday a temporary truce was declared in the town, where Ukrainian forces are fighting to hold it against surrounding rebels.
Convoys of buses travelled there to evacuate civilians who had been forced to shelter underground from the bombing.
They were escorted by monitors from the OSCE security watchdog, reported Reuters news agency.
Some 1.2 million Ukrainians have fled their homes since last April, when the rebels seized a big swathe of the Luhansk and Donetsk regions following Russia's annexation of Crimea.