MOSCOW (Reuters) - Russia's top natural gas producer Gazprom (>> Gazprom OAO) is considering making changes to contracts to keep its European customers on board if the West imposes sanctions on Russia over Ukraine, the Vedomosti newspaper said on Monday.

Citing a source close to Gazprom, the daily said the company may be willing to change its "take-or-pay" requirements, which make consumers pay for gas whether they take physical delivery or not. It did not give further details.

Gazprom declined to comment on the report.

Since President Vladimir Putin came to power 14 years ago, state owned Gazprom has increasingly a foreign policy tool, with Moscow using Russia's vast energy resources as a way to exert pressure on foreign powers.

Disputes over pricing with Ukraine have resulted in "gas wars", when Russia has turned off supplies.

Sergei Komlev, head of contracts structuring at Gazprom, told the Kommersant business daily that the company had been increasing its requirements under the "take-or pay" clause.

Analysts say Gazprom is unlikely to be hit hard by possible sanctions.

"Falling European production, coupled with the Asia-Pacific market swallowing up LNG volumes ... means that Europe does not have much flexibility in terms of cutting gas purchases from Russia, implying that Gazprom is most likely not vulnerable to possible EU economic sanctions," Alfa bank said in a note.

The United States and the European Union have warned Russia of sanctions as voters in Ukraine's Crimea region opted to join Russia in a referendum the EU said was illegal.

Gazprom meets almost a third of European Union's gas needs and has already agreed to cut prices for its key European clients, such as Germany's E.ON (>> E.ON SE) to try to maintain market share.

(Reporting by Vladimir Soldatkin, editing by Elizabeth Piper)

Stocks treated in this article : E.ON SE, Gazprom OAO