Ukraine's election body has voiced fears that it may be impossible to hold Sunday's presidential poll in the east, where a pro-Moscow insurgency is threatening to plunge the country into all-out civil war.

The warning came on Saturday as Ukraine's embattled government held a second round of "national unity" dialogue under a Western-backed plan to try to defuse the crisis, but failed to report any progress.

Moscow has insisted that Kiev must halt its monthlong offensive against the rebels before voting takes place, questioning the legitimacy of an election held under "the thunder of guns".

While Saturday's talks in the eastern city of Kharkiv involved a broad spectrum of Ukrainian politicians, including pro-Russians, no separatist leaders were invited.

"Round tables are beautiful things, but they won't solve anything," said Aleksandr Borodai, "prime minister" of the rebels' self-declared People's Republic of Donetsk, one of the rebel-held areas in the east.

The West sees next Sunday's election as crucial to defusing the crisis on Europe's eastern flank and preventing the recession-hit country from disintegrating further after Russia's annexation of Crimea.

But the Central Election Commission said it could not prepare for the vote in the east because of threats and "illegal actions" by separatists who have overrun more than a dozen towns and cities since early April.

It called on the authorities in Kiev to take urgent action to ensure security, saying that violence could prevent almost 2 million people from voting on Sunday, when some 36 million will be called to the polls.

Despite a monthlong offensive, the Ukrainian military has failed to wrest back control of the main industrial regions of Donetsk and Luhansk, where rebels have declared their own independent republics in defiance of Kiev and the West.

"Can elections held amid the thunder of guns really meet the democratic norms of the electoral process?" Russia's Foreign Ministry said in a statement, urging Kiev to immediately halt "punitive action against its own citizens".

It said Kiev was using the unity talks as a cover for aggressive action and urged Western nations to tell Kiev to "launch real and not phony work toward national reconciliation".

The election is expected to deliver victory to billionaire chocolate baron Petro Poroshenko, who enjoys a huge lead over former prime minister Yulia Tymoschenko.

The vote was called by the new leaders installed in Kiev after months of sometimes deadly pro-EU protests that led to the February ouster of Kremlin-backed president Viktor Yanukovych.

Fighting rages almost every night in the separatist regions, particularly around Sloviansk, the center of the insurrection.

(China Daily 05/19/2014 page11)