BP has signalled the end of its nine-year joint venture in Russia after confirming it would pursue the sale of the 50% shareholding.
TNK-BP, which is among the top 10 privately owned oil companies in the world, was built from the merger of BP's Russian oil and gas assets and those of four tycoons in the Alfa, Access/Renova group (AAR).
BP has notified AAR of its intention to sell its stake after receiving "unsolicited indications of interest" regarding the shareholding.
It comes in the week that one of the AAR billionaires, Mikhail Fridman, said the 50-50 ownership structure no longer served the interests of each party.
Having announced his resignation as chief executive on Monday, Mr Fridman told Russian newspaper Kommersant: "Everything is possible and realistic. We are open to proposals. There are a lot of different options."
BP and Russian oil company Rosneft last year offered to buy out AAR for about £20 billion as part of an attempt to salvage their Arctic exploration tie-up, which AAR had blocked.
TNK-BP has exploration and production assets as well as downstream marketing operations in Russia and Ukraine, alongside interests in Brazil, Venezuela and Vietnam.
BP shares were 4% higher at one stage.
Stuart Joyner, of Investec Bank, mentioned Rosneft and Gazprom as potential buyers and said his assumed price of 27 billion US dollars (£17.5 billion) would wipe out BP's debts, although part of any deal is likely to be in shares.
He added: "We do not think BP will make a step change in capital expenditure but we would expect the company to target assets in Africa and Brazil."