Kyiv said it expected to send its envoy, former President Leonid Kuchma, to the Belarusian capital Minsk on Saturday for talks aimed at shoring up a fragile truce agreement signed in September.
"We expect to sign a document that reinforces the Minsk Memorandum [of September] and the peace plan of presidents [Petro] Poroshenko and [Vladimir] Putin," Kuchma told the Interfax-Ukraine news agency.
A new round of negotiations planned for Friday under pressure from European envoys was postponed over disagreements about who should represent the pro-Russian separatists who have been waging an insurgency in eastern Ukraine since April.
Ukraine is insisting that rebel leaders Alexander Zakharchenko, who commands the insurgency in the Donetsk region, and Igor Plotnitsky, the leader of the separatist Lugansk region, should attend the talks in person and not just send representatives.
Last week, the insurgents pulled out of peace negotiations and announced the start of a new offensive aimed at extending their control over regions in Ukraine's southeast.
In a statement released on Friday, they said they would continue the offensive if the new talks failed.
"Should the negotiations collapse... the Donetsk and Lugansk People's republics reserve the right to pursue their offensive until the entire Donetsk and Lugansk regions are free of Ukrainian troops," negotiators for the rebels said.
They also said that the borders of rebel-held areas as agreed in Minsk in September should now be pushed back to match the current front. This would mean, according the separatists, some 500 square kilometers (200 square miles) more than laid out in the Minsk Memorandum.
Local officials and Kyiv military say 19 civilians and five Ukrainian soldiers have died in clashes since Thursday afternoon.
Five people were killed on Friday in the self-proclaimed rebel capital Donetsk in a mortar strike on a community center distributing aid, while two were killed when a mortar shell landed near a bus stop. Others died in sporadic artillery fire in the west of Donetsk.
Both sides have accused each other of the shelling.
Heavy fighting has also been reported around the railway hub of Debaltseve, which links Donetsk and Luhansk. The town of 25,000 people has been without electricity, running water and household gas for more than a week.
Kerry to visit
US Secretary of State John Kerry is to fly to Kyiv next week to discuss the crisis with Ukrainian leaders and pledge his country's support.
The rebels, who have been deploying a range of sophisticated armaments, claim to get all their weaponry from captured Ukrainian supplies.
The United Nations says more than 5,100 people have died so far in the nine-month conflict.
tj/bk (dpa, AFP, AP)