Kiev: Ukraine and the pro-Russian rebels said on Thursday they had agree to halt fire across the eastern war zone on December 9 under the terms of a Kremlin-brokered truce.
President Petro Poroshenko said the terms of the new ceasefire were already included in an earlier peace deal agreed with the help of European representatives in the Belarussian capital Minsk on September.
But the Minsk Agreement published at the time made no mention of a specific date on which the two sides were due to lay down their arms.
Poroshenko said Kiev had prepared "measures that should ensure the implementation of the Minsk Agreement concerning a Day of Silence that is due to begin on December 9."
A source in Poroshenko's office told AFP the president's statement meant that Ukraine would begin withdrawing heavy weapons from the eastern frontline on December 10 -- as long as the separatists also observe the truce.
The parliament speaker of the self-declared Donetsk People's Republic confirmed that the ceasefire was part of the Minsk deal.
"The (Minsk) group, which included our and Ukrainian military officials, as well as OSCE and Russian mediators, agreed to halt fire on December 9," Andrei Purgin told Russia's RIA Novosti state news agency.
But Purgin refused to say whether he thought this agreement would be able to end fighting that has killed more than 4,300 people in eight months.
Observers had assumed the September ceasefire was effective immediately and no indication was previously given that hostilities would only end in December.
Several truce deals announced in the course of the war were broken within a matter of days by both rebels and Ukrainian soldiers who refused to listen to their political leaders.
"I am not a prophet," Purgin was quoted as saying.
The head of the neighbouring self-proclaimed Lugansk People's Republic said a ceasefire that would begin in mid-December was discussed at the Minsk negotiations.
But he also stressed that no written agreement on a specific date was ever reached.
"I confirm that in the course of our discussion, this date was mentioned," Igor Plotnitsky told RIA Novosti.
"There was a verbal agreement (about a ceasefire) for around that date. But we do not have written confirmation of this yet," the Lugasnk separatist leader added.
"If we (the Kiev authorities) come here in the coming days and sign (such an agreement), then there will be a deal."
The September 5 agreement was meant to establish a 30-kilometre buffer zone between the fighters and grant limited self-rule to the separatists.
But hostilities only intensified after the two rebel regions held their own leadership polls on November 2 that were denounced by both Kiev and the West.