THE US Senate broke a two-decade deadlock last night by voting to open the Alaskan wildlife refuge to oil drilling, delivering President Bush a major victory.

Senators voted 51 to 49 to allow exploratory drilling in 1.5 million ecologically rich acres along the coastal plain of northeastern Alaska.

Oil firms have long eyed the 19 million acres of the Arctic Wildlife Refuge (ANWR), which they estimate as holding billions of barrels of oil.

However, efforts have always stalled in the Senate, where the agreement of 60 representatives is required to move issues to a vote. Environmentalists have maintained vehement opposition, arguing that drilling, even with new technology to lessen the impact, would do untold damage to calving caribou, polar bears, musk oxen and millions of migratory birds that use the plain.

This year, with an increased ten-vote Republican majority from November’s elections, party chiefs attached the issue to the budget, which cannot be filibustered and is subject to a straight majority vote. Seven moderate Republicans and the chamber’s sole independent joined 41 Democrats in trying to strip the issue out of the Budget. But three centrist Democrats joined 48 Republicans to keep it in. Republican supporters moved to avert fears of the environmental impact. “To explore to find out whether oil is there will absolutely do no damage to anything,” Pete Domenici, a Senator from New Mexico, said.

Mr Bush campaigned on the issue in 2000 and last year, describing it as a central plank of his energy policy that would reduce America’s reliance on imports. The US uses 21 million barrels of oil a day, 58 per cent of which is from overseas.

But opponents of ANWR drilling have argued that it would not produce more than one million barrels a day, having little impact on US imports. The issue of drilling in Alaska has been argued with new vehemence by proponents as the price of petrol has steadily risen over the past year. Oil climbed to a new trading high of $56.50 (£29.55) at the New York Mercantile Exchange yesterday and drivers across the country are complaining at having to pay more than $2 for a gallon of petrol.

Nevertheless, ANWR oil will not start appearing for another ten years. The next step is for the Government to raise $5 billion from oil companies in leasing fees to hunt for oil. Half the money would to go Alaska. Mr Bush said before last night’s vote that drilling in Alaska was “a way to get some additional reserves here at home on the books”.

John Kerry, the former Democratic presidential candidate and a veteran opponent of Alaskan oil exploration, called the budget measure a “Republican sneak attack” on the wildlife reserve. He said: “It’s a sad day when the voices of the American people are ignored and the Senate sells off America’s public lands to the highest bidder.”

But the issue is not home and dry. It has to appear in the final version of the Budget and could yet be derailed by Republican infighting, which plagued last year’s Budget. The Senate and House of Representatives are this year pursuing very different lists of spending cuts and tax cuts.

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