Khan said AAR, which already owns 50 per cent of TNK-BP, has been organising funding for the sale of the stake. It will make an offer by 17 October, Khan said.
He added that the offer for the stake will be “competitive”. It is thought the bid will be between $20bn and $25bn (£12.4bn).
BP is required to hold negotiations “in good faith” with fellow stakeholder AAR until 17 October, although a source close to the transaction said it was unlikely a deal would be agreed by then, and it would take “several months” for anything to be agreed.
Following the 17 October deadline, other suitors may then seek to strike a deal, creating the prospect of a bidding war.
Russian oil firm Rosneft is also considering a bid for the stake in TNK-BP, and talks between the British oil behemoth and both parties are understood to be underway.
Meanwhile, BP yesterday said its Devenick gas project in the North Sea had started successfully.
Production from the project, which cost BP and its partners around £650m, is due to peak next year at up to 100m cubic feet a day. It will boost Britain’s gas production by around three per cent next year, according to energy minister John Hayes.
Elsewhere, BP said gas flows from its Azeri Shah Deniz fields in Turkey were stopped last night after reports of a pipeline blast.