The Bush administration, in a closely watched conservation decision, ruled yesterday that it will not provide wilderness protection to millions of acres of Alaska's Tongass National Forest.

The decision by the U.S. Forest Service, rebuffing an effort by environmentalists to limit logging, formally affirms a recommendation the Forest Service made last May. Environmental groups said the decision could open more than a million acres of old-growth forest to logging, particularly if the administration or federal courts reverse the Clinton administration's restrictions on forest road building.

The Forest Service said no more than 676,000 acres could be opened to logging under any circumstance.

Denny Bschor, regional forester for Alaska, issued a "record of decision" that "recommends no more wilderness" be designated in the Tongass. Bschor said in a statement that "this plan will provide an economical supply of timber" using 4 percent of the 16.8 million acres in the Tongass.

Conservation groups said the ruling would dramatically expand logging in the Alaskan forest if Clinton's "roadless rule" is undone, as they expect. The Clinton rule would have prevented almost all logging in the Tongass, which contains nearly 30 percent of the world's unlogged coastal temperate rain forest. Congress has already set aside 6.4 million acres of the Tongass as wilderness, leaving about 9.5 million acres in dispute, of which only 1 or 2 million are commercially usable.

"This administration is bent on putting as much of the best of the last old growth of the Tongass on the chopping block," said Niel Lawrence, a lawyer with the Natural Resources Defense Council. "Today's decision clears the way for the Forest Service's announced intention to conduct over the next decade 49 huge timber sales."

Pamela Finney, a spokeswoman in the Forest Service's Juneau office, said that under no circumstance would there be logging on acres other than the 676,000 already designated, a "big chunk" of which is inaccessible because of the roadless rule. She said the service plans to offer 150 million board feet of timber each year, as set under a 1997 plan. "Those numbers have not changed," she said.

Yesterday's ruling was required by a federal court order directing the Forest Service to consider whether more of the Tongass should be designated as permanent wilderness.

In the huge spending bill enacted in February, Sen. Ted Stevens (R-Alaska), chairman of the Senate Appropriations Committee, attached a provision that would prevent further legal challenges to the 1997 Tongass management plan. Stevens dropped another provision that would have exempted parts of the Tongass from the roadless protections.