BP confirms that AAR's exclusivity period for TNK-BP ends

British oil firm BP confirmed on Friday that the 90 day period during which its partner, AAR, in its Russian oil venture TNK-BP had exclusive rights to make an offer for BP's share had ended.

"If and when BP reaches any agreement, it will make an announcement at the appropriate time," the company said in a statement.

TNK-BP is jointly owned by BP and the AAR consortium of four Soviet-born tycoons but looks set to be acquired by Russia's Rosneft .

Rosneft is poised to buy BP's 50 percent stake in TNK-BP, having already made an offer of around $28 billion to AAR, according to sources in London, Moscow and elsewhere.

The British oil company's board will meet on Friday to consider a cash and stock offer worth over $25 billion.

(Reporting by Sarah Young)