Rosneft said it might switch crude sales to rubles from dollars as the U.S. currency weakens, following similar statements by domestic rivals Gazprom and LUKoil.

"Our specialists are looking at all possibilities that could be beneficial for the company," Rosneft spokesman Nikolai Manvelov said Thursday. "Everything depends on economic viability," Manvelov said, declining to elaborate.

The dollar has dropped 10 percent this year against the euro, reducing the value of exports. OPEC members Iran and Venezuela have lobbied to abandon the dollar, a step Saudi Arabia rejected last month.

LUKoil may make the switch within two years, deputy chief executive Leonid Fedun said in New York on Wednesday.

"Selling for rubles is much more attractive," Fedun said. "Gazprom is considering introducing ruble-denominated contracts, and I think that technically Russian companies can do it by 2009 if the banks are ready."

Crude oil has surged 54 percent this year, contributing to an increase in inflation, which President Vladimir Putin calls one of the biggest threats to the economy's nine-year expansion. LUKoil has said the strengthening ruble eats into profits because costs are denominated in the local currency.

The ruble has gained about 8 percent this year against the dollar, while losing 3 percent versus the euro. The Central Bank manages the currency against a basket of the euro and the dollar.