* West threatens Russia with sanctions over Crimea vote
* Gazprom's shares down 1.1 pct, bucking a rising broader Moscow market
* European companies voiced support to deals with Gazprom (Adds detail, share price, source)
MOSCOW, March 17 Russia's top natural gas producer Gazprom is considering making changes to contracts to keep its European customers on board despite western sanctions on Russia over Ukraine, the Vedomosti newspaper said on Monday.
Citing a source close to Gazprom, the daily said the company might 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 become a foreign policy tool, with Moscow using Russia's vast energy resources as a way to exert pressure on foreign powers.
In disputes over gas pricing with Ukraine, through which pipelines carry around half of Russia's gas exports to Europe, Gazprom has twice in the past cut off supply, affecting other countries as well as Ukraine.
A source at Gazprom said talks on revising pricing and other conditions in the long-term contracts - a backbone of the energy giant's relations with its clients - are always under way.
"There are 20 countries in which Gazprom operates; the talks never stop. On average, a contract is revised every three years," the source said, brushing off suggestions about talks over sanctions. "Gazprom is not that flexible to react swiftly."
On the contrary, the Kommersant business daily quoted Sergei Komlev, head of contracts structuring at Gazprom, as saying that the company had been increasing its requirements under the "take-or pay" clause.
SANCTIONS LOOM SMALL
Gazprom's shares fell by 1.1 percent in the afternoon trade, bucking a 1.7 percent rise in the broader Moscow stock market .
Germany's Bild newspaper reported on Friday that visa bans threatened by the European Union and the United States in retaliation for Russia's seizure of Ukraine's Crimea region would include Gazprom head Alexei Miller and Rosneft head Igor Sechin.
But 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.
European Union foreign ministers have agreed to impose sanctions including travel bans and asset freezes on 21 officials from Russia and Ukraine, Lithuania's foreign minister said on Monday.
Gazprom meets almost a third of European Union's gas needs and has already agreed to cut prices for major European clients, such as Germany's E.ON to help maintain market share.
Some European companies have already voiced their support of cooperation with Gazprom despite possible sanctions.
BASF oil and gas unit Wintershall said last week the Ukraine crisis would not scupper an asset-swap agreement with Gazprom, which would give Russia greater access to gas trading and storage in Germany. (Reporting by Vladimir Soldatkin; editing by Elizabeth Piper and Jane Baird)