Alexander Zakharchenko and Igor Plotnitsky, the heads of the self-declared "People's Republics" of Donetsk and Luhansk, made the announcement in a joint statement on Thursday, with the assumption the Russian-supported peace plan will be signed during the negotiations in the Belarusian capital of Minsk.
The two leaders said they "are ready … at 15:00 (local time Friday) to order a ceasefire, if an agreement is reached and Ukrainian representatives sign a plan for the political settlement of the complicit."
The plan must "spell out in detail how to guarantee compliance with this [ceasefire] regime," the statement said.
Ukraine President Petro Poroshenko, meanwhile, said during a NATO summit in Wales Thursday that he would also order a truce.
"Tomorrow at 2 p.m. I will order the General Staff of the Armed Forces to cease fire, if the talks take place," he said.
Poroshenko has expressed high hopes for the upcoming negotiations. Both he and the Kremlin announced steps towards a potential deal on Wednesday.
NATO, Russia trade barbs
Ahead of the NATO summit, Secretary General Anders Fogh Rasmussen accused Russia of "attacking Ukraine" and called Moscow's seven-point peace plan to be negotiated Friday essentially meaningless.
"What counts is what is actually happening on the ground," the NATO boss said. "And we are still witnessing, unfortunately, Russian involvement in destabilizing the situation in eastern Ukraine."
Russia, meanwhile, accused NATO of undermining the peace effort by attempting to bring Ukraine in as a member of the trans-Atlantic military alliance.
Foreign Minister Sergey Lavrov said in comments carried by the Reuters news agency that attempts to end Ukraine's non-aligned status could "derail all efforts aimed at initiating a dialogue with the aim of ensuring national security."
Almost 2,600 people have died in the conflict since April, when pro-Moscow separatists began battling government forces shortly after Russia's annexation of Ukraine's Crimean peninsula in March.
dr/sb (Reuters, AFP, dpa, AP)