British oil company BP says it is in advanced talks about selling its stake in TNK-BP to Rosneft, Russia's state-controlled oil company, but that no agreement has been concluded.

Monday's statement from BP was its first confirmation that it was negotiating to sell its 50 percent stake in the TNK-BP joint venture to Rosneft.

Published reports have said BP was likely to take a stake of up to 20 percent in Rosneft as part of a deal. Rosneft is 75 percent owned by the Russian government.

BP shares opened 0.9 percent lower at 4.47 pounds.