Leaders from Ukraine, Russia, France and Germany were due to hold last-ditch peace talks Wednesday aimed at halting 10 months of conflict in east Ukraine that has claimed over 5,400 lives.

The crunch summit is the climax of a frantic diplomatic push by German Chancellor Angela Merkel and French President Francois Hollande to prevent the worst East-West crisis since the end of the Cold War from escalating.

For the first time since October, Ukrainian President Petro Poroshenko will come face-to-face with Russian strongman Vladimir Putin -- who Kiev and its Western allies accuse of masterminding the pro-Russian rebellion -- in an effort to thrash out a truce.

"Tomorrow's meeting in Minsk is one of the last chances to declare an unconditional ceasefire and withdraw heavy artillery," Poroshenko said in a statement Tuesday.

If the talks fail, US President Barack Obama has warned that Washington may decide to start providing arms to Ukraine, a step many European leaders have been desperately trying to avoid.

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.

- New proposals, old plans -

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 (200-square miles) 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.

Rebel rockets on Tuesday killed 15 people and wounded 63 around the government's military headquarters for the war-torn east in the town of Kramatorsk, well behind the volatile frontline.

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 (250 miles) 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.