GREAT FALLS, Mont. (AP) _ In a win for environmentalists, the U.S. Forest Service has ordered a ban on oil and gas drilling in a large section of the Lewis and Clark National Forest.

The so-called Rocky Mountain front includes the eastern edge of the Rockies from Glacier National Park, in northwestern Montana, almost to Helena in the west-central part of the state. Under the decision announced Tuesday by the forest service, drilling will be allowed in smaller mountain chains within the Lewis and Clark forest. Land under current leases will not be affected until the agreements expire.

The Forest Service originally proposed allowing leasing in parts of the Rocky Mountain Front _ in three drainage areas and in a 70-mile-long, mile-wide strip that would be accessible only through angled drilling.

But Gloria Flora, supervisor of Lewis and Clark National Forest, said public protest helped persuade her to toughen the restrictions.

Public comments received during the 2 1/2 years the draft was being composed were overwhelmingly opposed to development along the Front, and a poll for the Great Falls Tribune this month found 52 percent of Montanans opposed.

The Rocky Mountain front, with its combination of jagged mountains and rolling plains, is a haven for wildlife, including grizzly bears. Geologists say untold reserves of oil and gas lie beneath the surface, but how much is anyone's guess.

Opponents have 45 days to file an appeal with the Forest Service.

Gail Abercrombie, executive director of the Montana Petroleum Association, said the industry group was ``extremely disappointed'' but the decision hasn't been made yet whether to appeal.

``They've been beating their heads against the closed doors so long that I don't know if they want to go ahead,'' she said. She predicted companies will go elsewhere to explore.

``Public lands decisions seem to be taking on the life of a popularity contest,'' Ms. Abercrombie said.

Sen. Max Baucus, D-Mont., has tried to include the front in past wilderness bills to no avail.

``The Rocky Mountain front is a special place for all of us,'' Baucus said in a statement. ``Its value goes well beyond that of any oil or minerals we could extract from its soil. This decision protects the front for our children and grandchildren.''