"I am ready to announce a complete and unconditional ceasefire any time to stop the rising civilian casualties," Ukrainian President Petro Poroshenko said Saturday in Munich, where world leaders were meeting to try and find a way out of the conflict.

Poroshenko said Kyiv was prepared to sign a truce "in a few hours or days" if Russia was also willing.

Kyiv struck a ceasefire deal - complete with a demilitarized buffer zone - with the pro-Russia rebels in Minsk last September, but that agreement was never properly implemented and fell apart completely after the rebels launched a new offensive in January.

The Minsk agreement is expected to form the basis of a new peace push by France and Germany, but there are also likely to be some important differences.

"There is a bit more detail around how it will be implemented and more of a roadmap on timing," a senior US State Department official said after meetings between the United States and leaders from Germany and Ukraine.

"Implementation… is where this has got into trouble in the past, so a big part of the effort is to flesh that out in a way that may be more successful."

Poroshenko stressed he was also open to discussing the size and contours of a proposed buffer zone separating the combatants, and was prepared to put the question of federalization to a referendum.

Separatist representatives had said earlier that they would only agree to a ceasefire that acknowledged their current frontline, which includes significant territorial gains.

Poroshenko has made a passionate plea for world leaders to help end the conflict

New rebel offensive?

Fighting in eastern Ukraine continued unabated into the weekend, with the country's military reporting Saturday that five soldiers had been killed and 26 injured in the past 24 hours. Officials also said five civilians had been killed. According to the United Nations, some 5,400 people have died in fighting in eastern Ukraine since April.

Ukraine's military also said rebels had stepped up shelling of government forces and were sending tanks, rocket launchers, armored personnel carriers and "accumulating forces for further offensive operations on Debaltseve and Mariupol."

Debaltseve has been at the center of fierce fighting over the past week as rebels try to surround government troops that still control the strategic town.

Revive the peace plan

The intensified fighting has prompted a flurry of diplomatic exchanges. German Foreign Minister Frank-Walter Steinmeier said it would be clear in "two or three days" whether the Franco-German peace initiative had a chance of succeeding.

"We hope to succeed in making some progress," he said, adding that although Germany and France were facilitating talks, "the important decisions must be made in Moscow and Kyiv."

His Russian counterpart, Sergei Lavrov, said once Kyiv and Ukrainian separatists came to an agreement on the details of a peace deal, "Russia will be among those parties that will guarantee the implementation of this agreement."

"But you can only guarantee what has already been achieved," he added.

Poroshenko and Russian President Vladimir Putin are set to discuss the plan with the leaders of Germany and France by phone on Sunday.

nm/cmk (dpa, Reuters, AFP AP)