* Rosneft calls a possible visa ban 'stupid, petty'
* Both CEOs of the two companies travel extensively
* Companies have vast overseas operations
By Vladimir Soldatkin and Olesya Astakhova
MOSCOW, March 14 (Reuters) - A possible ban on visas for the heads of Russia's two biggest energy firms, Rosneft and Gazprom, may hamper their international partnerships but also harm their Western partners and push the two towards the East.
Rosneft, the world's largest listed oil company by production and reserves, and Gazprom, the top natural gas producer, rely heavily on overseas markets for their sales. Their chief executives travel abroad frequently to promote their businesses and strike deals with international partners.
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.
European officials earlier said that the EU list includes 120 to 130 names of senior Russian officials who could be subjected to travel bans and asset freezes.
Both Sechin and Miller worked together with Russian President Vladimir Putin in the 1990s and are the members of what is seen as Putin's inner circle.
"This is stupid, petty and obvious sabotage of themselves most of all," Rosneft spokesman Mikhail Leontyev said, when asked about the threat of EU visa sanctions. "I think this would primarily affect Rosneft's business partners in the West in an extraordinary way."
Miller frequently travels to Europe and on Thursday was in Berlin to celebrate an anniversary of cooperation with German utility E.ON.
Sechin also travels frequently. Sources at Rosneft said he would embark on a long tour to Asia next week with stops in India, Vietnam, South Korea and Japan.
Gazprom declined to comment, saying it would wait for an official statement, rather than rely on media speculation.
Disruptions in energy supplies from Russia as a result of a visa ban or other sanctions could lead to a jump in oil and gas prices, which could damage the fragile recovery of the European economy.
Gazprom last year accounted for more than 15 percent of global gas production and reserves and earned export revenues of $163 billion. It controls a third of Europe's gas market. Russia also supplies Europe with a quarter of its oil, mainly from Rosneft.
"European business is closely tied up with Rosneft and Gazprom," said Sergei Vakhrameyev, an analyst with Ankorinvest brokerage in Moscow. "If (the visa ban report) is true, it would hamper partnerships between the companies."
Rosneft has agreements with the U.S.'s Exxon Mobil, Italy's ENI and Norway's Statoil on exploring oil and gas in Russia's Arctic. It holds a 50 percent stake in four Ruhr Oel refineries in Germany and 21 percent in Italian refinery Saras. Last December, it agreed to buy much of Morgan Stanley's physical oil-trading business.
"Deals are in danger of being scrapped (in the case of sanctions)," Vakhrameyev said.
Western companies with significant interests in Russian energy stand to lose.
The UK's BP owns 19.75 percent of Rosneft. Shell is part of the Gazprom-led Sakhalin-2 project in Russia's Pacific, which includes Russia's sole liquefied natural gas export plant.
Western banks hold most of the $90 billion in combined debts of Rosneft and Gazprom.
Disintegrating relations with the West could push Russia's energy giants further to the East and encourage them to do more business with China, which earlier this year overtook Germany as Russia's single largest oil buyer.
"It impedes (Rosneft/Gazprom's) ability to do some deals and is annoying and uncomfortable, but it isn't crippling," said Bruce Bower, an analyst at Moscow-based hedge fund Verno, about the threat of visa sanctions.
He added that the move would accelerate Russia's tilt toward the Far East, which started with the building of pipelines to China.
Rosneft has been increasing oil exports to China and targets delivery of nearly 1 million barrels per day there, up from around 300,000 bpd last year. The rise in oil exports to Asia has led to cuts in oil exports to Europe.