OIL prices jumped today after BP was forced to begin a production shutdown at the biggest oil field in the United States.

The closure process, which is expected to take several days to complete, is likely to reduce oil production by 400,000 barrels a day - equivalent to some eight per cent of oil production in the US.

News of the shutdown of Alaska's Prudhoe Bay plant, which BP said was due to pipeline corrosion, lifted the price of crude oil for September delivery by around one dollar to dollars 75.75 in Asian trading this morning. The market has also been affected by the continuing violence in the Middle East.

BP, already part of a criminal probe into a much bigger Alaskan pipeline rupture in March, was unable to estimate when output might resume at Prudhoe.

The closure is the latest incident to hit the British energy giant's Alaskan operations, and deals another blow to its US image following a fatal refinery explosion last year and a trading scandal.

Newly appointed BP America chairman and president Bob Malone said: "We regret that it is necessary to take this action and we apologise to the nation and the State of Alaska for the adverse impacts it will cause."

Prudhoe Bay is operated by a BP-led group that includes oil majors ConocoPhillips and Exxon Mobil, which was involved in Alaska's biggest oil spill when the 11 million-gallon Exxon Valdez tanker was grounded in 1989.