A spokesman for BP was quoted by The Daily Telegraph in London as saying Rosneft offered between $25 billion and $28 billion for its stake in its Russian joint venture, TNK-BP.
"We are reviewing our options including any offers that we have received," the spokesman said.
Alfa Access Renova, a business entity representing the business interests of Russian tycoons, holds an equity share in the joint venture with BP. Rosneft, the Financial Times reports, may be interested in taking on AAR's stake in the venture as well. With only BP's half, however, Rosneft would have a stake in more oil production than supermajors Exxon Mobil or Royal Dutch Shell, the report adds.
Russian President Vladimir Putin expressed his support for the deal in September when he met with BP's Chief Executive Officer Bob Dudley. Dudley was the top executive at TNK-BP before leaving in 2008. The Russian side of the joint venture had complained he was favoring British interests in his position.
Russian Energy Minister Alexander Novak told state-run news agency RIA Novosti that Rosneft's action wouldn't create market problems.
"There will be no monopoly position as there is quite tight competition in a large market," he said.
BP shareholders meet Friday.