TNK-BP accounts for 25% of BP's global production and 10% of its profits.

BP denies the shareholder agreement with AAR, the holding company of the Russian billionaires led by Mikhailo Fridman through which they control 50% of TNK-BP, was breached by the new agreement with Rosneft.

Rosneft chose BP for its expertise in operating in hostile offshore environments—skills that TNK-BP, which is an onshore producer, lacks.

A BP spokesman, quoted in the Wall Street Journal on Saturday, said that the company's law firm, Linklaters, had sent a letter to AAR's lawyers, Skadden, Arps, Slate, Meagher & Flom LLP, suggesting the two sides seek "expedited arbitration" in Sweden, under the terms of a conflict-resolution procedure set out in the TNK-BP shareholder agreement.

"We said it's in everyone's interests to have a speedy resolution of the issues," said the spokesman according to the Wall Street Journal.

A hearing in London's High Court on AAR's application for an injunction to block the BP-Rosneft deal is scheduled for Tuesday.

But tyhe Wall Street Journal said "observers say BP's attempt to fast-track a resolution of the dispute quickly will stumble on a key obstacle: No-one at BP appears to know what AAR actually wants and what it will take for it to settle. It's still unclear whether AAR is seeking to participate in the Rosneft-BP partnership or to stymie it completely."