UPDATE 1-Gazprom says gas transit via Ukraine to Europe may fall to 10-15 bcm per year

per year@ (Adds detail)

MOSCOW, April 10 (Reuters) - Future Russian gas transit flows through Ukraine to Europe may be between 10 and 15 billion cubic metres per year, Alexei Miller, head of Russian gas giant Gazprom, said on Tuesday, which is a significant decline from current levels.

Miller issued his comments after German Chancellor Angela Merkel said that the planned new Nord Stream 2 pipeline between Russia and Germany could not go ahead without clarity on Ukraine's role as a transit route for gas.

"We have never raised an issue about abandoning the Ukrainian transit. However, the Russian resource base has been moving northward and there won't be the same resources in the central gas transportation corridor as it was in the past," Miller said in a statement.

"That's why a certain transit could still be in place, in the amount of 10-15 bcm per year, but the Ukrainian side has to explain the viability of the new transit contract," he said.

He did not give a time frame for when the transit could be 10-15 bcm a year.

Ukraine has been a key route for carrying Russian gas to Europe where it supplies around a third of gas needs, but Moscow and Kiev have clashed frequently over energy.

Last year, the transit amounted to more than 93 bcm, while Gazprom's total exports to Europe and Turkey reached an all-time high of 194 bcm.

Last year, Ukraine earned around $3 billion in Russian gas transit fees.

Gazprom said last month it would terminate its gas contracts with Ukraine after it lost a court case, escalating a dispute which had left Ukraine struggling to stay warm and which the European Union said could threaten gas flows to Europe.

A Stockholm arbitration court ordered Gazprom in February to pay more than $2.5 billion to Ukrainian energy firm Naftogaz - a ruling meant to conclude a long legal battle that has run alongside Ukraine's broader political stand-off with Russia.

Gazprom wants to bypass Ukraine as an export route and plans to build two more undersea gas pipelines to Europe: TurkStream to Turkey and Nord Stream 2 to Germany.

Eastern European and Baltic states fear Nord Stream 2, planned to run through the Baltic Sea, could increase reliance on Russian gas and undermine Ukraine's role as a gas transit route.

The plans for the pipelines were given new impetus after relations between Moscow and Kiev plunged as Russia-leaning president Viktor Yanukovich fled Ukraine in 2014 following street protests and a pro-Moscow revolt subsequently flared in eastern Ukraine.

The current deal between Russia and Ukraine on gas purchases and transit expires at the end of 2019 and Kiev has been worrying about losing its transfer fees for shipping the Russian gas westwards to Europe. (Reporting by Vladimir Soldatkin; Editing by Adrian Croft)