A Russian state firm has offered to buy BP's half share in its huge oil joint venture, according to reports.
If a state firm acquires the stake, that would signal a dramatic reorganisation of Russia's oil industry - the world's largest - just weeks after Vladimir Putin returned to the presidency, reported Reuters.
Selling out would see BP abandon nearly a third of its oil production after years of maintaining that its giant investment in Russia was a cornerstone of its strategy.
But it would also cut it loose from hostile partners, raise around USD 30 billion and free it from an investment that had restricted its ability to pursue other opportunities in Russia.
BP did not say who had made the "unsolicited approaches" to buy the giant stake, but a source close to the matter said one of the Russian state-owned oil and gas firms was involved.
TNK-BP is Russia's third largest oil producer, and BP's stake represents one of the biggest foreign investments ever made in the country. It has earned BP huge profits but has long been plagued by acrimonious legal battles between BP and its Russian partners, the AAR consortium of billionaires.
Putin, who returned to the presidency he occupied from 2000-2008, has long discouraged foreign companies owning strategic assets, which limited BP-TNK's ability to expand.
For BP, selling out would mean giving up annual dividends which hit USD 3.7 billion last year and losing around 30 percent of its oil and gas production, but would give it a cash pile to explore higher-growth ventures, perhaps even in Russia.
Funds raised would help to fund the ongoing cost of cleaning up the 2010 Gulf of Mexico oil spill.
Given the Kremlin's desire to exert influence over the oil sector, analysts and bankers immediately pointed towards state-backed players, especially Rosneft, as the most likely buyers.
"We believe that the eventual buyer will have to be Russia - a 2 million barrels per day company (1 million barrels per day net to BP) is just too strategic for Russia to let fall into foreign hands," said Oswald Clint, oil analyst at Bernstein.
A source close to Rosneft denied it was behind the bid. Another possible bidder could be Rosneftegaz, a state holding company that controls Rosneft.
Last week, powerful former deputy prime minister Igor Sechin was appointed chief executive of Rosneft with - a source close to the group said - a goal to transform the company into a national champion capable of competing on a global scale.
AAR said it had received notice from BP of intent to sell the stake, and repeated its own longstanding offer to increase its holdings.
BP's relationship with AAR is governed by a complex shareholders' agreement, but analysts said this was unlikely to hinder a BP sale. BP said any deal would comply with it.