By Yereth Rosen

ANCHORAGE, Alaska (Reuters) - A planned study ofpossible new wilderness protections for the Arctic NationalWildlife Refuge has sparked a furor in Alaska, where energycompanies have long dreamed of tapping oil reserves beneath itsvast coastal plain home to herds of migrating animals.

The U.S. Fish and Wildlife Service effort announced thisweek is part of a sweeping review of a land-management plan forwhat is the second-largest national wildlife refuge in theUnited States.

The agency stresses that its work is just starting and thata formal draft is not expected until next year.

But the oil industry and its political allies regard it asa prelude to an attempt to keep the refuge off-limits to energyproduction for good by formally declaring its remote coastaltundra as wilderness.

"Alaska will not allow the federal government to lock upmore land without a fight," Governor Sean Parnell said thisweek.

The Alaska Wilderness League, for its part, accuses oilcompanies of trying to destroy a refuge that represents theonly place on Alaska's North Slope that is legislatively closedto development.

"The Arctic Refuge is one of the last true wilderness areasleft in the United States -- some places are just too specialto sacrifice to oil and gas development," said Cindy Shogan,the league's executive director.

Established 50 years ago in the northeast corner of Alaska,ANWR occupies 19.3 million acres,stretching from saltwater marshes of the Beaufort Sea on itsnorthern edge to the spruce, birch and aspen forests in theBrooks Range's southern foothills.

Its wilderness plan was last revised in 1988, eight yearsafter Congress expanded the refuge to its current size andeffectively closed all of it to energy development.

ACT OF CONGRESS

The sweeping review is only in its preliminary stages, witha draft plan expected next year, said Bruce Woods, spokesmanfor the U.S. Fish and Wildlife Service in Alaska.

"We haven't proposed anything for wilderness. We're notnearly ready for that," Woods said Thursday.

Ultimately, an act of Congress is required to open thecoastal plain to oil drilling or designate it as wilderness --the most protective classification that can be applied onfederally owned lands.

But Alaska Senator Lisa Murkowski says the study is "ablatant political move by the administration and clearlyviolates the promise of no more administrative wildernessdesignations in Alaska."

"This is a waste of time and taxpayer money -- and it's aproposed waste of the oil and natural gas resources that belongto all Americans," she said in a statement.

Conservation groups have their own supporters on CapitolHill. A group of U.S. senators is proposing to establish formalwilderness designation for the coastal plain, a move that wouldmake oil drilling in the refuge all the more remote.

BIOLOGICAL HEART

For both sides, the crux of the matter is the 1.5million-acre coastal plain.

Drilling supporters say it could hold 11 billion barrels ofoil or more. Opponents say that narrow coastal section is thebiological heart of the refuge because it is the calvinggrounds for the region's vulnerable caribou herd.

Right now, nearly half of the overall refuge is protectedas formal wilderness. No such protections exist for the coastalplain. But Congress has not authorized oil drilling there,either.

Review of the Arctic refuge comes amid similar managementrewrites for all of Alaska's 16 national wildlife refuges.

But the initial phase of the management review for theArctic refuge, launched in the spring, has drawn more than90,000 public comments, he said. In contrast, reviews for otherrefuges have elicited dozens or a few hundred public comments.

The last time Congress voted to lift prohibitions on oildevelopment in the Arctic refuge was during Republican controlof the House and the Senate in 1996.The measure was vetoed by President Bill Clinton. (Editing by Xavier Briand)