WASHINGTON — Conspicuous by its absence from the sweeping energy bill that President Bush has championed and will sign today is his top energy priority: opening an Alaska wildlife refuge to oil drilling.

But the fight over the future of the Arctic National Wildlife Refuge will flare anew in Congress next month, and drilling advocates say they have their best chance in more than two decades of making it happen.

Tapping what is believed to be at least 10 billion barrels of oil within the refuge's 1.5 million-acre coastal plain has been the centerpiece of Bush's energy agenda dating to his first presidential campaign in 2000. He has said repeatedly that the oil is important to the nation's national and economic security.

But the idea that drilling proponents might win has outraged environmentalists, who see the region as a pristine refuge where caribou, polar bears, migratory birds and other wildlife thrive and should be protected.

A coalition of Democrats and moderate Republicans in the Senate has repeatedly used the threat of a filibuster to thwart attempts to open the refuge to energy development.

"If we had put [Arctic drilling] in the bill, we wouldn't be here," said Sen. Pete Domenici, R-N.M., celebrating passage of the energy bill that Bush plans to sign in a ceremony in Albuquerque, N.M. The bill never could have mustered the 60 votes needed to overcome a certain Senate filibuster over ANWR, he said.

But drilling advocates have a backup plan that is expected to unfold in mid-September.

Domenici said he will include a provision authorizing ANWR drilling as part of the budget process. Unlike other legislation, budget bills are not subject to filibuster, so only 51 votes would be needed in the Senate for the ANWR provision to clear Congress and be signed into law.

Just such a tactic was used a decade ago when Congress approved ANWR drilling as part of the budget process, only to see the measure vetoed by President Clinton.

Sen. Lisa Murkowski, R-Alaska, said her state's delegation is determined to push for opening the refuge, calling it "the final component" of a nation energy plan that she hopes will be put in place later this year.

Alaska and the federal government would split the proceeds from oil leases, which the Congressional Budget Office has estimated at $5 billion over five years.

This expected revenue is at the heart of the strategy that drilling supporters plan to pursue to end more than 20 years of debate over access to ANWR's oil. The budget would assume $2.5 billion in federal revenue from ANWR lease sales, beginning in 2007. That, in turn would allow lawmakers to draft an accompanying document authorizing such drilling — a "reconciliation" document, which is not subject to filibuster and when signed by the president would have the force of law.

It's "backdoor budget chicanery," said Rep. Edward Markey, D-Mass., an ANWR-drilling opponent.

"By shoehorning the Arctic refuge into the budget, they are making an end run around the legislative process, knowing it cannot pass the Senate any other way."