Citing unpaid bills, Russia cut off gas flows to Kiev in mid-June, adding to East-West tensions triggered by Russia's annexation of Ukraine's Crimea and conflict in Russian-speaking eastern Ukraine.

Last Tuesday, the latest round of talks between Russia and Ukraine, brokered by the Commission, to try to resolve the gas supply dispute ended without a deal.

Since then, relations between Russia and Ukraine may have been further complicated by elections on Sunday in which pro-Western parties emerged as the winners.

To try to resolve the gas dispute, further trilateral negotiations take place in Brussels on Wednesday.

The Commission confirmed a preparatory telephone call between Kiev and Brussels would be held on Monday.

"It is part of the preparation for the trilateral gas meeting on Wednesday," a Commission official said on condition of anonymity.

The negotiations last week broke down over Ukraine's inability to assure Russia it could pay off outstanding debt for unpaid bills and provide cash upfront for future suppplies.

Russian President Vladimir Putin issued a plea to the European Union and United States on Friday, asking them to help cash-strapped Ukraine raise funds to pay for Russian gas purchases and warning about escalation of the gas crisis.

(Reporting by Barbara Lewis; editing by Adrian Croft)