KIEV (AFP) - Ukraine's new Western-backed President Petro Poroshenko vowed on Sunday to halt by the end of the week nearly two months of bloodshed in the separatist east that have threatened the very survival of the ex-Soviet state.
But his pledge was immediately dismissed as political grandstanding by insurgents who have proclaimed independence in two vital industrial regions that are now seeking a formal invitation to join Russia.
And Mr Poroshenko himself did not spell out how he intended to make the pro-Russian gunmen comply with the ceasefire or whether he would order a full military withdrawal from the restive Donetsk and Lugansk regions.
"We must end the fighting this week," Mr Poroshenko said following a round of talks with Moscow's ambassador to Kiev and an envoy from the Vienna-based Organisation for Security and Cooperation in Europe (OSCE).
"For me, every day in which people die, every day in which Ukraine pays such a high price, is unacceptable."
The 48-year-old candy magnate - dubbed the "chocolate king" - delivered a forceful inauguration address the day before in which he vowed never to accept Russia's seizure of Crimea or give up on Ukraine's new pro-European course.
He flatly rejected dialogue with "gangsters and killers" who both Kiev and the West accuse the Kremlin of backing.
But the political veteran also said separatists who had "no blood on their hands" would be offered safe passage back to Russia.
A top leader in the self-proclaimed "Donetsk People's Republic" said he doubted Mr Poroshenko's sincerity and was still mobilising his troops.
"We do not know what exactly Poroshenko said concerning an end to the fighting, but we somehow doubt that he will be withdrawing troops," Donetsk "deputy governor" Mr Andriy Purgin told Russia's Interfax news agency.
"We are continuing to mobilise, preparing volunteers for the defence of Donetsk."
Europe's worst security crisis in decades has now plunged East-West relations into a Cold War-style standoff and left the ex-Soviet country of 46 million facing disintegration and economic collapse.
Daily battles in the region of nearly seven million people have claimed more than 200 lives since mid-April and continued unabated on Sunday.
A Ukrainian military source told AFP that gunmen had staged a series of unsuccessful raids late Saturday and early Sunday on an airport in the Russian-border city of Lugansk.
The source said Ukrainian forces suffered no casualties but could not say if any militants had been killed.
The insurgents lost more than 40 fighters - most of them Russian nationals - while briefly seizing the main international hub in the neighbouring industrial city of Donetsk in late May.
Ukrainian media also reported intense fighting involving mortar fire and air assaults being waged in the region's rebel stronghold of Slavyansk.
Mr Poroshenko said the first step in his peace plan involved restoring "the Ukrainian border so that the safety of each Ukrainian citizen is guaranteed."
Both militants and weapons have been crossing into Ukraine from Russia in growing numbers without any visible efforts to stop them by either President Vladimir Putin or his generals.
But the Russian leader appeared to respond to US pressure on Saturday by demanding that the FSB security service step up the border region's defence.
Russia's seizure of Crimea in March set off a wave of nationalistic fervour that saw Mr Putin's approval rating hit 80 per cent.
But the threat of further economic sanctions and a stampede by Western investors exiting Russia have also drawn questions about the long-term costs of Mr Putin's combative stance.
"With his Ukrainian escapade, Vladimir Putin embroiled the entire country in a reckless geopolitical game, making the Russian people hostage to his own ambitions," former Russian prime minister and heavy Putin critic Mikhail Kasyanov wrote in a blog post.
"The game is over, and Putin's primary job now is to minimise his political losses and save face." Recent studies conducted in Ukraine's eastern rustbelt also show a majority opposing independence or an outright merger with Russia.
Mr Poroshenko was the top vote-getter in both the Donetsk and Lugansk districts despite his vow to use force if necessary to keep Ukraine whole.
"As strange as it may seem, it is these very imperialistic ambitions of Putin that made the people of Ukraine start to increasingly demonstrate the unity of a hardened nation," respected military analyst Valentyn Badrak wrote in Kiev's Dzerkalo Tyzhnia weekly.
Mr Poroshenko's other immediate challenge involves averting an imminent Russian gas cut that could further cripple an economy that last year had already slipped into its second extended recession since 2009.
Ukraine won a vital reprieve last week when Russia pushed back until Tuesday an ultimatum for Kiev to deliver billions of dollars in overdue payments or see its fuel supplies cut.
Moscow demanded the money after stripping Ukraine of price discounts it had awarded the ousted pro-Kremlin regime - a decision denounced by the new Kiev leaders as a form of "economic aggression".
About 15 per cent of Europe's gas from Russia transits through Ukraine and neighbouring countries are deeply concerned about a repeat of interruptions that took place in 2006 and 2009.
A top EU envoy is now urgently seeking a compromise that could save 18 member states from seeing their deliveries start dwindling this week.
The Russian energy ministry said the final round of EU-mediated talks will be held on Monday evening in Brussels.