MINSK: Ukraine was set Friday to sign a Kremlin-backed truce with insurgents that could halt nearly five months of bloodshed but whose failure would unleash new Western sanctions against Russia.
But even before the peace talks opened in the Belarussian capital Minsk, renewed combat was erupting on the edge of the strategic port of Mariupol, the latest flashpoint in the conflict that has plunged East-West relations to a post Cold War low.
AFP correspondents also reported heavy bombardments overnight in Donetsk, the main rebel-held city in eastern Ukraine, further highlighting the fragility of any ceasefire deal.
The seven-point blueprint -- unveiled by Russian President Vladimir Putin this week after telephone talks with his Ukrainian opposite number Petro Poroshenko -- would require government forces to retreat from much of the industrial regions of Donetsk and Lugansk.
But Poroshenko said he held out "very careful optimism" that peace could return to the splintered ex-Soviet country, and vowed to order a halt to hostilities 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. If that happens, I assure you that Ukraine (will) find a peace solution within days."
NATO leaders voiced strong support for Ukraine at a 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.
But Britain's foreign secretary said Friday the measures could be lifted in the event of a ceasefire.
"If there is a ceasefire, if it is signed and if it is then implemented, we can then look at lifting sanctions off," Philip Hammond said at the NATO summit.
Any truce deal would however 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.
Poroshenko had vowed after his May election to crush the rebellion -- a mission that seemed on the verge of success until NATO reported last week that more than 1,000 Russian soldiers had flooded across the border with heavy weapons in support of a sweeping counter-offensive by the insurgents.
The rebels now appeared to have set their sights on Mariupol, whose seizure would help link Russia with the Crimean peninsula annexed by Moscow in March.
The Kremlin accuses the Western military alliance of concocting the evidence in order to expand its own presence along Russia's western frontier.
But Western allies suspect Putin of trying to throw Kiev's leaders -- in power since the February ouster of a Moscow-backed administration -- permanently off balance and keep the east's huge industrial base dependent on Russian trade.
"While talking about peace, Russia has not made one single step to make peace possible," NATO chief Anders Fogh Rasmussen observed.
But "if we are witnessing genuine efforts for a political solution, I would welcome it".
The US Department of Defence said the 20,000 Russian troops it suspects are massed on the Ukrainian border were "more lethal" than ever before.
EU leaders are considering new reprisals against Russia that would keep its biggest energy and defence corporations from raising money in the West.
They are also holding early discussions about boycotting the 2018 football World Cup in Russia -- an event especially dear to Putin's heart.
NATO has already agreed to set up new funds to help Ukraine's military effort in a conflict that has seen around 2,600 people killed and more than half a million forced from their homes since mid-April.
The alliance is also expected to approve plans to position troops and military equipment in eastern Europe to reassure ex-Soviet bloc member states unnerved by Russia's actions in Ukraine.
"A verified ceasefire probably would slow the imposition of new EU and US sanctions," the Eurasia Group political risk consultancy said.
"But Russia is highly unlikely to cut support to the separatists, and Western governments will likely escalate sanctions in the coming weeks."
Putin's push for peace would leave the rebels -- fighting what they claim is anti-Russian discrimination by Poroshenko and his more nationalist government -- in effective control of a region that accounts for one-sixth of Ukraine's population and a whopping quarter percent of its exports.
A Kremlin account of the ceasefire plan said it requires "Ukrainian armed forces units to withdraw to a distance that would make it impossible to fire on populated areas using artillery and all types of multiple launch rocket systems."
But it also establishes a "safe zone" that one rebel negotiator said should enable the militias to hold on to territories stretching to the very edges of the two separatist districts.
Poroshenko himself has never spelled out the terms of the truce.
But signs of discontent among his allies were highlighted by Prime Minister Arseny Yatsenyuk's contention that Putin drafted the agreement to "pull the wool over the eyes of the international community" and avoid further sanctions. (AFP)