The stake is held in the form of American Depository Receipts.BP intends to dispose of the stake through a bookbuilding exercise comprising both an equity sale and exchangeable bond issue.

"It not yet finalised. It will be somewhere between a quarter and a third sold directly and the rest will be monetised via the exchangeable bond," Peter Henshaw, BP Amoco (Moscow) director (external affairs) said.

Credit Suisse First Boston and UBS Warburg are acting as the joint bookrunners.

The planned sale does not affect BP's other agreements with Lukoil, which is a long-standing partner. The joint venture, Lukarco and its 12.5 per cent of the Caspian Pipeline Consortium also came with the Arco deal.

BP also co-operates with Lukoil in the Caspian through the Azerbaijan International Operating Co - which produces around 100,000 barrels of oil per day in the Caspian - as well as the Shah Deniz gas prospect in Azerbaijan.

Nor does the move affect BP's intention to stay in Russia, which produces around 9 per cent of the world's oil and has one-third of global gas reserves.

"BP plans to remain as a leading foreign investor in Russian energy ventures, both upsteam and downstream," Mr Alexander added.

Among BP's Russian assets are a 10 per cent stake in oil firm Sidanco as well as a 25 per cent stake in Rusia Petroleum, the major player in Kovyktinskoye, a huge gas field in Irkutsk near Mongolia, which aims to export gas to China and Korea.

On the downstream side, BP owns 27 retail petrol stations in Moscow and aims to expand its presence in the next three years.

BP's shares, which have underperformed the oil and gas sector by around 5 per cent over the past 12 months, were up 1/2 penny at 595-1/2P At 1138 GMT.