TNK-BP Chief Financial Officer James Owen quit yesterday, saying a dispute between BP Plc and its billionaire partners in the Russian oil venture had made it difficult for him to work independently, as his role demands.

Owen tendered his resignation to Chief Executive Officer Robert Dudley yesterday, the company said. He will leave at the end of this month.

TNK-BP, a 50-50 venture between BP and a group of billionaires known collectively as AAR, is embroiled in a dispute over strategy and management. BP, which relies on the company for almost a quarter of its production, is struggling to maintain control of the company.

"I greatly regret that we are losing Jim," Dudley said. "He will be very hard to replace."

Dudley left Russia last month citing "sustained harassment" in receiving permission to work in Russia and perform his duties, Bloomberg News said.

BP CEO Tony Hayward and billionaire Mikhail Fridman met in Prague on July 30 to seek a resolution to the dispute after the battle for control of the company, Russia's third-biggest crude producer, intensified last month.

The investors in the venture are Fridman and fellow billionaires German Khan, Viktor Vekselberg and Len Blavatnik. Fridman and Vekselberg have said BP treats TNK-BP like a subsidiary and has constrained growth, which BP denies.

Hayward said July 29 that BP would not be "intimidated by strong-arm tactics" and vowed to defend its rights at TNK-BP.

BP last month pulled its remaining 60 employees contracted to work at the venture from Russia, as a minority shareholder in TNK-BP's traded unit sought to overturn the agreement covering their services. Vekselberg, a TNK-BP executive as well as shareholder, demanded last week that the vacancies be filled.