By Alexander Kolyandr 

MOSCOW--The European Union has failed to broker a truce to resolve the long-running natural gas dispute between Russia and Ukraine at high-profile talks Friday, though the Kremlin said gas supply to Europe should be safe this winter.

EU energy chief Günther Oettinger traveled to Moscow to discuss a possible interim deal with Russian Energy Minister Alexander Novak ahead of three-way talks, which it is hoped will take place next week.

The talks coincide with a sharp escalation in the conflict between Russia and Ukraine. On Thursday, Ukraine accused Russia of invading the country, saying Russian troops seized the coastal town of Novoazovsk and other villages along the border.

At Friday's gas talks, Russia repeated its previous offer to sell gas to Ukraine at a discount of $100 per 1,000 cubic meters of gas, Mr. Novak said after meeting Mr. Oettinger.

The offer puts the price of a 1,000 cubic meters at about $386

The Ukraine government rejected the offer several hours after the meeting, as it did in June, saying it is longing for a deal derived from the spot market price rather than an oil-dependent long-term supply price formula, which Gazprom favors.

"We see this price as discriminatory," Ukraine Energy Minister Yuriy Prodan said in a statement, adding that Kiev has made several offers, some of them with the European Commission.

Mr. Novak said Russia is still open for gas talks with Ukraine, but so far Russia has rejected all Ukraine's proposals.

However, no date for a new meeting has been set, while Ukraine must pay at least $1.45 billion of its debt to Russia's gas monopoly OAO Gazprom before any talks on the restructuring of the rest of $5.3 billion debt can start, he said.

The EU has been trying to revive negotiations since they broke down last June, when Gazprom halted its delivery of gas supplies to Ukraine over billions in unpaid gas bills from Kiev. Ukraine has said Moscow unfairly raised gas prices.

Time is of the essence for all sides. Gazprom is losing valuable income by continuing to withhold gas deliveries to one of its biggest and most lucrative markets--around half of the government's revenue comes from oil and gas exports.

For Ukraine's government, the onset of cold winter months could exacerbate an already very fragile outlook, with the economy battered by months of turmoil and civil war continuing in the east of the country. The government said last month that businesses might be forced to reduce energy consumption in the case of gas shortages. In the worst-case scenario, people could be left without heat and power in their homes.

The EU, for its part, is determined to avoid a repeat of 2009 and 2012, when pricing disputes also led to supply disruptions in some EU countries at the height of winter. Ukraine is the main transit route for Russian gas supplies to the 28-member bloc, which relies on Russia for over a third of its gas imports. Six countries, including Bulgaria and Slovakia, are wholly dependent on Gazprom for their gas supplies. However, all the sides say now that the flow of gas won't be interrupted.

Mr. Oettinger and Mr. Novak said a some kind of a temporary solution of the price dispute should be found to enable Ukraine to pump about 10 billion cubic meters of gas into its underground storage to prevent shortages this winter.

The two energy chiefs said European gas supply isn't in danger of being cut off, as all sides remain committed to a secure supply of energy.

Vanessa Mock in Brussels contributed to this article.

Write to Alexander Kolyandr at Alexander.Kolyandr@wsj.com

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