By Andrew Callus

LONDON (Reuters) - BP has said executives and fellow shareholders in its Russian oil joint venture TNK-BP should stop taking decisions which the British group believes need board approval, according to two sources familiar with the matter.

The letter, sent to TNK-BP this week, exposed fraught tension between BP, Alfa-Access-Renova - the other co-owner of the Russian oil company, and its management following BP's announcement it may sell out.

AAR, owned by four oligarchs, and BP joined forces in TNK-BP in 2003. Relationships have been rocky with each accusing the other of breaking a confidential shareholder agreement.

Earlier this month, BP said it had received expressions of interest for its stake in TNK-BP and would look to sell. Sources said Rosneftgaz could buy the stake, allowing the Kremlin to reassert its control over the oil sector.

BP's letter arrived just ahead of a visit to institutional investors in London by one of AAR's owners, Mikhail Fridman, to tout his plans for a future structure of the TNK-BP, Russia's third largest oil producer.

On Thursday, the Financial Times quoted people familiar with the matter as saying Fridman had proposed two scenarios.

One option involved AAR selling its 50 percent stake to BP for cash and shares, which would leave the oligarchs with significant shareholdings in the British oil major.

The second would see AAR buying half of BP's stake in TNK-BP. BP has said it did not want to be a minority shareholder in TNK-BP, which provides almost a third of its oil production.

Sources close to AAR have said the consortium would be willing to buy out BP for $25 billion. The FT quoted a person close to AAR as saying the stake was worth about $7 billion after potential litigation costs.

Fridman stepped down as CEO of TNK-BP in May, days before BP said it could sell out.

BP paid $8 billion in 2003 for its half of TNK-BP, a hugely profitable investment that has yielded $19 billion dividends.

(Editing by Dan Lalor)