BP is to use up to $8 billion of the proceeds from the sale of its stake in TNK-BP, a joint venture with state-controlled Russian oil group Rosneft.

A pair of transactions valued at $56 billion to buy out the co-owners of TNK-BP gives the Kremlin an industry giant in Rosneft while still retaining BP's expertise.

Outline terms of deal have been signed that gets BP out of a troubled joint venture and that will eventually leave it holding a 19.75% stake in the state backed Russian oil company.

If the state-backed Russian oil giant does acquire TNK-BP from co-owners BP and AAR, a group of Soviet-born oligarchs, it would leap to the top of the ranks of the world's oil majors.

The billionaires who co-own Russian oil venture TNK-BP have reportedly agreed to sell their stake to the state-backed Russian oil giant Rosneft.