MINSK - Fighting raged Friday as Ukraine prepared to sign a Kremlin-backed truce with insurgents that could halt five months of bloodshed but whose failure would unleash new Western sanctions against Russia.
The tense hours preceding the peace talks that opened in the Belarussian capital Minsk saw the rebels advance to the very edge of the industrial port of Mariupol - the latest strategic flashpoint in a conflict that has plunged East-West ties to a post-Cold War low.
AFP correspondents also reported overnight shelling that killed five civilians in the main rebel bastion of Donetsk, a city that government forces had all but encircled until being beaten back by separatists last week.
The seven-point ceasefire plan - unveiled Tuesday by Russian President Vladimir Putin after telephone talks with Ukrainian counterpart Petro Poroshenko - calls on both sides to halt "offensive operations" and for government troops to retreat from much of the eastern industrial regions of Donetsk and Lugansk.
Poroshenko said he held out "very careful optimism" that peace could return to the splintered ex-Soviet country once the pact is signed at the European-brokered talks.
"The only thing we need now for peace and stability is just two main things," Poroshenko said Thursday on the sidelines of the NATO summit in Wales. "First, that Russia withdraw its troops; and second, to close the border."
NATO leaders reaffirmed their unanimous backing for Ukraine at their two-day meeting that has focused largely on Russia's new expansionist threat.
EU and US officials have said sanctions against Russia would be announced Friday in response to a major escalation of Moscow's military support to the rebels that has raised fears of another land grab after the annexation of Crimea in March.
But British Foreign Secretary Philip Hammond said the measures could be lifted in the event of a sustained truce. "If there is a ceasefire, if it is signed and if it is then implemented, we can then look at lifting sanctions off," he said at the NATO meeting.
Any ceasefire would nonetheless leave the political status of Ukraine's economically-vital east uncertain and expose Poroshenko to charges that he had signed his government's surrender to Russian troops.