Moscow - Russia will be ready to hold more talks with Ukraine on its natural gas supplies only when Kiev pays its gas debt to Moscow, Deputy Energy Minister Anatoly Yanovsky said on Monday.

“We want contract liabilities to be fulfilled... To continue talks, the debt should be paid,” Yanovsky told reporters.

Moscow says Kiev owes it $3.51 billion for gas, and has told Ukraine it must pay in advance for its gas from June.

Russia's top natural gas producer, Gazprom, supplies about 30 percent of the gas consumed in Europe, and ships about half of that via Ukraine.

Russia's Energy Ministry said last week Gazprom would send a preliminary bill for June before May 16 and deliver gas only in volumes that reflected what payments it had received before May 31.

Ukraine wants to change the conditions of a 2009 contract, negotiated by an earlier government.

This deal locked Kiev into buying a set volume, whether it needs it or not, at $485 per 1,000 cubic metres - the highest price paid by any client in Europe.

Moscow dropped the price to $268.5 after President Viktor Yanukovich turned his back on a trade and association agreement with the European Union last year but reinstated the original price after Yanukovich was ousted in February.

On Monday, Gazprom said gas flow to Europe remained stable. - Reuters