Washington ? Conspicuous by its absence in 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 with drilling advocates saying 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 back to his first presidential campaign in 2000. Bush has repeatedly said the oil is important to the nation’s national and economic security.

But the idea that drilling proponents might win has produced outrage among environmentalists, who see the region as a refuge where wildlife thrive and should be protected.

A coalition of most Democrats and a handful of moderate Republicans has thwarted attempts to open the refuge to energy development through the power of the Senate filibuster.

“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.

A section of land inside the Arctic National Wildlife Refuge in Alaska, proposed to be used for oil exploration by the Bush administration, is shown in this undated file photo. Conspicuous by its absence in the energy bill that President Bush will sign today is his top energy priority - the opening of this Alaska wildlife refuge to oil drilling. But the fight over the future of the Arctic refuge will flare anew in Congress in September.

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 a budget procedure that is immune to filibuster. A similar maneuver is being planned in the House, although the final strategy is still being worked out.

“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,” said Rep. Edward Markey, D-Mass., an ANWR drilling opponent.

Environmentalists are gearing up for a fight, hitting community events during the summer August doldrums when Congress is in recess, hoping to rally public sentiment against drilling.