Ukrainian President Petro Poroshenko has extended a week-long ceasefire with pro-Russian separatists in the east for another three days.
He said he was hoping for progress on his peace plan.
Some rebel leaders in the Donetsk and Luhansk regions said they would observe the truce, but others rejected it.
Mr Poroshenko's announcement came hours after he had signed a landmark EU trade pact - the issue that has been the trigger of the recent crisis.
He said it was a "historic" moment, but Russia warned of "consequences" and that Ukraine would split in two.
The deadline for the ceasefire to expire was Friday at 22:00 local time (19:00 GMT).
Separatists in the east held talks on Friday with mediators, including Ukraine's former President Leonid Kuchma, Moscow's ambassador in Ukraine and the Organization for Security and Co-operation in Europe (OSCE).
The leader of the self-declared "Donetsk People's Republic" in the east, Aleksander Boroday, said the new truce would be observed until 30 June.
However, two other senior rebels in the Donetsk region, Pavlo Gubarev and Igor Girkin, were quoted by local media as saying they rejected the truce.
In Kiev, Mr Poroshenko met top security and defence officials to discuss the truce after returning from Brussels.
A statement was later posted on the Ukrainian presidential website confirming the truce until 19:00 GMT 30 June.
The document pointed to a policy statement on Ukraine, issued by the European Council on Friday which set out key steps it expected to happen by Monday.
They include the return of three key checkpoints to Ukrainian forces and the "launch of substantial negotiations on the implementation of President Poroshenko's peace plan".
Russian Foreign Minister Sergei Lavrov earlier said he would welcome an extension, but not if it were simply an ultimatum for separatists to lay down their arms.
Russian President Vladimir Putin has insisted on a long-term ceasefire to allow for negotiations between the Ukrainian government and separatists, urging Mr Poroshenko to embark on a "path of peace, dialogue and accord".
Mr Putin said: "There is bloodshed in the south-east Ukraine, humanitarian catastrophe, tens of thousands of refugees have to look for shelter, on Russian territory."
Mr Poroshenko set out a 15-point peace plan on 20 June. It involves decentralising power and holding early local and parliamentary elections.
It also proposes the creation of a 10km (six-mile) buffer zone on the Ukrainian-Russian border, and a safe corridor for pro-Russian separatists to leave the conflict areas.
German Chancellor Angela Merkel warned Russia the EU was prepared for "drastic measures" if there was no speedy progress on Mr Poroshenko's peace plan.
French President Francois Hollande said more measures would be taken if there was no progress after Sunday, when he and Mrs Merkel will speak to Mr Putin by phone.
Fighting is said to have continued in some areas of eastern Ukraine despite the ceasefire.
But rebels have now released four international observers captured more than a month ago.
More than 420 people have been killed in fighting between pro-Russia rebels and government forces in eastern Ukraine since mid-April, the UN estimates.
The separatists have declared independence, claiming that extremists have taken power in Kiev. Their move followed Russia's annexation of Ukraine's Crimea region.
Earlier on Friday in Brussels, Mr Poroshenko hailed the 1,200-page EU Association Agreement as a turning point, describing it as a "symbol of faith and unbreakable will".
Analysis: Steve Rosenberg, BBC News Moscow
There is a general sense of irritation or perhaps even anger here that Moscow has failed to convince countries like Ukraine, Moldova and Georgia not to sign this historic free trade deal with the EU.
Moscow has economic concerns about these deals - it is worried that the Russian market could be flooded by cheap goods from the EU that would hit Russian producers.
More pressing for Moscow are the geopolitical concerns here - the whole idea of former Soviet states, countries that Moscow still views as being within its sphere of influence, drifting towards Europe and one day possibly becoming part of the EU - that really grates with Moscow, particularly in the case of Ukraine.
Moldova and Georgia also signed the agreement.
"What a great day! It is a historic day, maybe the most important day since independence," Mr Poroshenko said.
But Mr Putin said that "attempts to force on the Ukrainian people an artificial choice between Europe and Russia brought [a split] to society, a painful internal confrontation".
The refusal of Mr Poroshenko's predecessor, Viktor Yanukovych, to sign the EU deal, under pressure from Russia, had led to protests in Kiev and his eventual overthrow this year.
Russian Deputy Foreign Minister Grigory Karasin said there would "undoubtedly be serious consequences for Ukraine's and Moldova's signing".
The Kremlin immediately said it would take "all the necessary measures" against Ukraine.
Russia has warned it will hit Ukraine with punishing trade restrictions.