The Interior Department might act soon on its year-old proposal to make the polar bear the first species to be listed as threatened with extinction because of melting ice from a warming planet.

Both sides agree that conservationists finally have the poster species they have sought to use the Endangered Species Act as a lever to force federal limits on the greenhouse gases linked to global warming and possibly to battle smokestack industry projects far from the Arctic.

“All animals are equal, but some animals are more equal than others,” said Kassie Siegel, an attorney with the nonprofit Center for Biological Diversity. “And then there is the polar bear.”

Even Frank Luntz, the political consultant who advised President Bush six years ago to focus on discrediting the science of global warming and refer to it as “climate change,” has recognised the bear’s potency. In an interview on the environmental Web site Grist org, he said the public has a “soft side” for the bear.

Federal government scientists have presented increasingly compelling evidence that the top predator at the top of the world is doomed if the polar regions get warmer and sea ice continues to melt as forecast. Two-thirds of the population could be gone by mid-century if current trends continue, experts say. Bears are beholden to sea ice, where they perch so they can pounce on seals, their primary food.

Images pop up regularly of scrawny, exhausted bears dragging themselves onto ice floes looking like bones covered in sodden white rugs. So do reports of struggling bears swimming wearily in open water. It’s a shocking contrast to the pop-culture image: smiling animated bears guzzling Coke in commercials or fluffy stand-ins adorning children’s bedrooms.

But the energy industry is worried. At least one part of the environmental community believes the bear’s listing would provide the leverage to stop a coal-fired power plant thousands of miles away from the Arctic.

Sen. Jim Inhofe, R-Okla., who is known for his skepticism about global-warming measures, recently asked US Fish and Wildlife Service Director H. Dale Hall whether listing the polar bear could be used to halt the construction of a power plant in Oklahoma City. “The Endangered Species Act is not the vehicle to reach out and demand all of the things that need to happen to address climate change,” Hall said, to Inhofe’s apparent satisfaction.

Andrew E. Wetzler, director of the Natural Resources Defense Council’s endangered species project, said Hall misunderstands the legal principles underlying the act. If the builders of a coal-fired plant needed a federal permit, they probably would have to show how its emissions would not erode the polar bear’s habitat or jeopardise its survival, Wetzler said.

Several conservation groups have filed a lawsuit and threatened a second one to force the listing of the bear. Already, they have sued to nullify oil exploration leases in the Chukchi Sea, arguing that the bear’s plight got short shrift during environmental reviews.

Opposing forces representing the oil and gas industry, manufacturing and property-rights advocates have begun threatening counter-suits over the potential listing. “This is going to be the mother of all test cases,” said Alison Rieser, a lawyer and ocean policy professor at the University of Hawaii.