Ukraine's president has announced a new initiative to try to shore up a truce with pro-Russian rebels in the east.
Both sides signed a ceasefire in Minsk, Belarus, on 5 September, but there have been constant breaches.
Fighting since then has cost the lives of almost 1,000 people, the UN says.
President Petro Poroshenko said troops would observe a "day of silence" on Tuesday to try to kick-start the Minsk deal. Rebel leaders were quoted by the RIA news agency as agreeing.
However, this has not been independently confirmed.
Earlier this week, another truce agreement set to start on Friday fell apart within hours of being agreed amid new shelling.
Since the conflict began in April, more than 4,300 people have died with almost one million displaced, the UN says.
The Ukrainian presidential website confirmed that security officials had met "to discuss measures to implement the Minsk accords", with a "day of silence" on Tuesday.
A presidential source told AFP news agency that Ukraine would then start withdrawing heavy weapons from the frontline on 10 December, if the separatists in the eastern regions of Donetsk and Luhansk observed the ceasefire.
One of the pro-Russian separatist leaders in Donetsk, Andrei Purgin, confirmed the agreement with the RIA news agency.
It also quoted the head of the self-proclaimed Luhansk People's Republic, Igor Plotnitsky, as saying a verbal agreement was in place.
However, he said there was no "written confirmation".
The Minsk agreement projected a 30km (18 mile) military buffer zone in the east and limited self-rule for the separatists.
However both Luhansk and Donetsk then held leadership elections on 2 November that Ukraine and the West refused to recognise.
The Ukraine crisis began a year ago, when then-President Viktor Yanukovych abandoned an agreement on closer trade ties with EU in favour of closer co-operation with Russia.
This decision sparked pro-EU protests in the capital Kiev, eventually toppling Mr Yanukovych in February.
In the weeks that followed, Russia annexed Crimea, in Ukraine's south, and pro-Russian separatists took control of Donetsk and Luhansk, declaring independence.
The crisis has caused a serious rift between Russia and Ukraine's Western supporters.
The Kremlin has repeatedly denied Ukrainian and Western accusations that it has sent tanks and troops to the war-torn region to help the rebels.
In his annual state-of-the nation address to Russia's parliament on Thursday, President Vladimir Putin accused Western governments of seeking to raise a new "iron curtain" around Russia.
He condemned economic sanctions imposed over the annexation of Crimea, saying: "Every time someone believes Russia has become too strong, independent, these instruments get applied immediately."
Mr Putin expressed no regrets over the move, saying the territory had a "sacred meaning" for Russia.
Speaking in Basel in Switzerland later, US Secretary of State John Kerry said the West did not seek confrontation with Russia.
"No-one gains from this confrontation... It is not our design or desire that we see a Russia isolated through its own actions," Mr Kerry said.
Russia could rebuild trust, he said, by withdrawing support for separatists in eastern Ukraine.