BP PLC's (BP.LN) partners in TNK-BP said Monday they are seeking to raise at least $20 billion to buy out the U.K. oil giant's 50% stake in the Russian joint venture, potentially setting up competition with OAO Rosneft (ROSN.RS) for the stake.

The loan would be raised against the income from the lucrative TNK-BP venture, said Stan Polovets, chief executive of Alfa Access Renova, the consortium that holds the Soviet-born billionaire's stake in the company.
AAR last week hired Rothschild Group to arrange syndication for the loan, he said. Rothschild declined to comment.

AAR's potential all-cash offer could lead to a serious competition to purchase BP's stake in TNK-BP, which analysts have estimated is worth around $25 billion, with Russian oil giant Rosneft as the rival bidder.

BP confirmed in September it is in talks with Rosneft over a deal that could involve payment in a mixture of cash and Rosneft shares.

The Russian government has given mixed signals over who should take the stake in one of country's largest oil producers. The Kremlin appears to back the Rosneft bid, while the prime minister's office hasn't ruled out allowing
AAR to buy BP's stake.

"The government has no objections toward
AAR increasing its stake in TNK-BP," said Russian Deputy Prime Minister Arkady Dvorkovich, in comments published in Russian newspaper Kommersant and confirmed by his office. Referring to Rosneft's potential offer, Mr. Dvorkovich said the government must not expand its direct involvement in the economy, including through the purchase of private companies by state ones.

BP has been in talks with both
AAR and Rosneft over the acquisition of BP's half of TNK-BP since July. AAR 's initial offer to buy half of BP's stake was rebuffed by the U.K. firm, which maintains it is only interested in selling its entire shareholding.

BP is obligated under its agreement with
AAR to negotiate in good faith for a period of 90 days that started on July 18 and ends Oct. 17, after which it can sell to whomever it chooses.

In September, BP's top executives met with Russian President Vladimir Putin and Rosneft Chief Executive Igor Sechin, who said the British company intended to invest in Rosneft if it was successful in its attempt to sell its stake in TNK-BP.

The Rosneft deal could be more attractive for BP, which has its sights on a long-coveted arctic oil exploration deal with the Russian company, analysts have said. However, a cash offer from
AAR could appeal to BP's shareholders, some of whom would like to see the company reduce its exposure to Russia and pay out a special dividend.