The leaders of Ukraine, Russia, Germany and France will sign a document following all-night talks in Minsk on solving the Ukraine conflict, a diplomatic source told Reuters on Thursday.
The source would not provide details of the nature of the document.
The tortuous talks had dragged on till dawn as the four leaders tussled over a plan to end 10 months of conflict in east Ukraine that has killed over 5,400 people.
The negotiations opened on Wednesday evening with a brief handshake between arch-foes Ukrainian President Petro Poroshenko and Russian leader Vladimir Putin, who were meeting for the first time since October.
The four-way meeting with German Chancellor Angela Merkel and French President François Hollande in the Belarusian capital was the climax of a frantic European diplomatic drive aimed at stopping the worst East-West crisis since the end of the Cold War from escalating.
Underscoring the urgency, the number of those reported killed in the hours before the make-or-break talks rose to at least 49 as rebels said another civilian was killed when a hospital in their bastion Donetsk was shelled as the leaders met, following the earlier deaths of 16 people in a devastating rocket attack.
“Today the peace process for Ukraine is all about Minsk and I hope that the meeting will fulfil our best expectations,” Poroshenko told host Belarussian leader Alexander Lukashenko ahead of the talks.
By 6 am local time (0300 GMT) the marathon negotiations had passed the ten-hour mark and the four leaders remained shut in an ornate meeting room in Minsk’s opulent presidential palace without their advisors.
“Everybody is yawning but they are still arguing,” a source close to one of the delegations told AFP shortly before the agreement was announced.
France’s Hollande had said prior to the meeting in Minsk that he and Merkel would “try everything right to the end” to try to get something from the last-ditch meeting.
Earlier, a senior Ukrainian diplomat told AFP on condition of anonymity that the talks were making “progress” but also proving “very hard”.
On Tuesday, Obama spoke to Putin by phone and sought to pressure him to rein in the rebels and embrace the chance for peace.
"If Russia continues its aggressive actions in Ukraine, including by sending troops, weapons, and financing to support the separatists, the costs for Russia will rise," the White House said.
Western diplomats, however, warn the warring sides remain deadlocked over key issues, and that there is no guarantee of reaching a conclusive accord that might end resurgent fighting.
"Nothing is certain yet, and holding a summit does not mean it will lead to success," German Foreign Minister Frank-Walter Steinmeier said.
The plan to be discussed is based largely on flouted peace agreements between Kiev and the rebels in September. The hope is that, at minimum, a ceasefire to halt fighting that has killed hundreds of civilians in recent weeks can be agreed upon in Minsk.
In lower-level talks in the city on Tuesday ahead of the summit, the separatists submitted their settlement proposals but warned that "it is too soon to speak about a ceasefire".
A key sticking point is whether a new deal will extend rebel control over some 500-square kilometres of territory seized over the past month.
As the peace bid headed to the wire, fighting has raged on the ground with both sides trying to strengthen their hands at the negotiating table.
Just hours before the talks in Minsk were set to begin Wednesday, a shell hit a bus station in the centre of the rebel-controlled city of Donetsk, in eastern Ukraine, killing at least one person.
At least 19 soldiers have also been killed in fighting in east Ukraine since early Tuesday, a Kiev defence official said on Wednesday, including five in a rocket attack on regional capital Kramatorsk.
"Nineteen soldiers were killed in the last 24 hours and 78 wounded," military spokesman Vladyslav Seleznyov told journalists in Kiev, after officials had already announced the death of five troops in Tuesday's attack on Kramatorsk.
Insurgent fighters have been battling for weeks to take the key transport hub of Debaltseve, while Ukrainian forces on Tuesday captured ground around the key port city of Mariupol.
Kiev is desperate to get Putin – who has watched Western sanctions and low oil prices batter the Russian economy – to put pen to paper on a deal.
The former KGB spy has consistently told Kiev it needs to reach an agreement with the rebels, not with him.
Moscow is pushing for the separatist-held territories to be granted a large degree of autonomy, while Ukraine is demanding it gets control back over some 400 kilometres of its border with Russia.
Kiev and the West accuse Putin of pouring soldiers and troops into Ukraine to spearhead the insurgency, but Moscow flatly denies it is behind the fighting.