AFP/Kiev
French, German and Ukrainian leaders are planning a summit with Russian President Vladimir Putin for Wednesday in a frantic bid to halt escalating bloodshed in east Ukraine.
The four leaders talked by phone on Sunday as part of urgent efforts to achieve a "comprehensive settlement" in the conflict between Ukrainian forces and pro-Russian rebels, Berlin said.
German Chancellor Angela Merkel and French President Francois Hollande have been carrying out frantic diplomacy in recent days, jetting to Kiev for talks with Ukrainian President Petro Poroshenko and to Moscow to meet Putin, accused by the West of masterminding the 10-month-old conflict.
Putin said the summit planned in the Belarussian capital Minsk would only take place if the leaders agreed on a "number of points" by then.
"We will be aiming for Wednesday, if by that time we manage to agree on a number of points which we've been intensely discussing lately," Putin told Belarus President Alexander Lukashenko.
Foreign ministry officials will hold preparatory talks in Berlin on Monday, Ukraine said, when Merkel meets US President Barack Obama at the White House.
A meeting between mediators from the Organization for Security and Co-operation in Europe, Ukrainian and Russian representatives and the rebels is also expected to take place Tuesday, Ukraine's presidency said.
During the latest push to keep peace hopes alive, the leaders "continued to work on a package of measures to achieve a comprehensive settlement of the conflict in eastern Ukraine," Berlin said of Sunday's phone conversation about what Hollande has called "one of the last chances" for peace.
The Ukrainian presidency said the leaders "expect that their efforts during the Minsk meeting will lead to an immediate and unconditional bilateral ceasefire".
Fresh fighting in the former Soviet republic claimed 12 civilian lives, separatist and Kiev authorities said, with 12 Ukrainian troops also killed in the last 24 hours.
A previous peace deal agreed in Minsk in September has since been largely ignored, with fighting escalating in recent weeks and the Ukraine government accusing the rebels of massing troops for fresh offensives.
French Foreign Minister Laurent Fabius told the Munich Security Conference that "what Germany and France are seeking right now is not peace on paper, but peace on the ground."
- 'Additional' US assistance -
With the US apparently moving towards providing out-gunned Ukrainian troops with hi-tech weapons despite some European opposition, US Secretary of State John Kerry insisted in Munich that the US and Europe remained united.
"Let me assure everybody, there is no division, there is no split," Kerry said.
"We all agree that this challenge will not end through military means (but) the longer it takes, the more the off-ramps are avoided, the more we will be forced to raise the costs on Russia and its proxies."
"International borders must not, cannot be changed by force in Europe or anywhere else," Kerry said.
German Foreign Minister Frank-Walter Steinmeier conceded that "we remain far removed from a solution to the Ukraine conflict" despite the most recent flurry of diplomacy.
"Europe can only have permanent security with, not against Russia," said Steinmeier.
A senior State Department official has said the new European peace plan is based on September's widely flouted ceasefire deal, but admitted the initiative was still "very much in flux and evolution".
Hollande told French TV station France 2 that the proposal includes the creation of a 50- to 70-kilometre (31- to 43-mile) demilitarised zone based around the current frontline.
But this idea appeared to face opposition from the Ukrainian president, who has lost territory to the rebels since the Minsk deal. "There is only one line, and that's the line from the Minsk agreement," Petro Poroshenko said.
- 'There's no war' -
Putin, meanwhile, said Russia is not at war and does not want war with anyone, but lashed out at Western sanctions imposed as the Ukraine crisis has deepened.
"There's no war, thank God. But there is definitely an attempt to curb our development," Putin said prior to the leaders' phone call.
Far from the diplomatic exchanges, fighting raged in eastern Ukraine, where some 5,400 people have been killed since the start of the conflict in April and Kiev says rebels are massing their forces for fresh offensives.
It said the separatists were sending fresh tanks, armoured personnel carriers and multiple rocket launcher systems to the Debaltseve region and Granitne, around 35 kilometres (20 miles) northeast of the city of Mariupol.
The town of Debaltseve -- mid-way between rebel centres Donetsk and Lugansk -- has been the focus of fierce fighting for over a week as insurgents try to encircle government troops holding the strategic railway hub.