Anchorage, Alaska (AP) -- An environmental group is pressing ahead with efforts to declare Alaska's polar bears threatened under the Endangered Species Act, with the larger agenda of forcing the Bush administration to confront global warming.

The federal government repeatedly has denied scientific evidence of global warming, said Kassie Siegel of the Center for Biological Diversity in Joshua Tree, Calif. A determination that polar bears are threatened would change that.

"It will force the Bush administration to confront the reality of climate change in the Arctic," Siegel said.

If successful, polar bears would be the first mammal to be protected due to climate change.

The center in February filed a 154-page formal petition with the federal government seeking to list the polar bear as threatened. The petition blames global warming for melting sea ice habitat.

Polar bears feed primarily on ringed seals and use sea ice for feeding, mating and maternity denning. Polar bears wait out the summer on land, using stored fat until they can return to the ice.

A finding that global warming is the direct cause of harm to a threatened species would trigger provisions of the Endangered Species Act to protect the animal, such as limits on utilities and industry producing greenhouse gasses, not only in Alaska but throughout the country.

The U.S. Fish and Wildlife Service, the agency responsible for polar bears, failed to meet a 90-day deadline set out in law for an initial determination of the petition's merit. The agency now is under a 12-month deadline determining whether an animal should be listed as threatened, Siegel said.

Fish and Wildlife Service Alaska regional director Rowan W. Gould said in a letter to Siegel that the agency spends significant funding complying with court orders and settlement agreements and can only address so many petitions yearly.

The crush of work, including more than 50 pending petitions, has kept the agency from meeting its deadline, which is 90 days "or as practicable," said Fish and Wildlife Service spokesman Chris Tollefson. "Basically, we have more to do that we have resources or people to do it."

The 12-month deadline is more firm, Tollefson said.

"We're going to certainly to our best to meet that," he said.

Listing polar bears as threatened, and determining that global warming was killing them, would require the federal government to use the "best science available" to reducing global warming, Siegel said.

"The Bush administration will be compelled to consider the science," Siegel said.

The Endangered Species Act would require the Interior Department to draft a recovery plan.

"That will say, what does that species need to not decline toward extinction and to in fact recover and become stable so it will become de-listed?" she said. "That also would have to be a science-based plan."

When approving permits for development, federal agencies would be required to consult with the department on its effects on polar bears, Siegel said.

The Center for Biological Diversity, joined by the Natural Resources Defense Council and Greenpeace, this month announced their intent to sue to have bears listed as threatened, another formal step in the Endangered Species Act.

Andrew Derocher, a University of Alberta biologist and chairman of the polar bear specialist group for the World Conservation Union's Species Survival Commission, said the group downgraded polar bear status worldwide from "least concern" to "vulnerable," in June, citing climatic warming.

Collectively, the best scientists and managers internationally believe there is a strong likelihood of a 30 percent decline in bear population within 35 to 50 years, with the principal cause tied to climate change, Derocher said.

A joint announcement last month by the University of Colorado's National Snow and Ice Data Center, NASA and the University of Washington declared a "stunning reduction in Arctic sea ice at the end of the northern summer."

The center concluded that if current rates of decline in sea ice continue, the summertime Arctic could be completely ice-free well before the end of this century.

Alaska polar bear populations currently are healthy, according to federal researchers. Summer has seen significant reductions, said polar bear expert Steve Amstrup of the U.S. Geological Service in Anchorage. But winter ice though thinner, and tending to be less than a year old, has not changed much, Amstrup said.

The results are more alarming at lower latitudes. A collaborative study by American and Canadian researchers in western Hudson Bay demonstrate the bear population has been declining steadily, from 1,200 bears to less than 1,000, Amstrup said.

"The cause of that decline is apparently the earlier retreat of the sea ice, which means bears are stuck on land for a longer period of time than they used to be," Amstrup said.

Derocher said he would like to believe the warming is merely part of a cycle, but he doubts it.

"I hope we're wrong," Derocher said. "I haven't seen the evidence to suggest this is a natural pattern."

If the researchers are right, a major ecosystem could disappear.

"To do it in the Arctic would be fairly catastrophic," Derocher said. "There aren't many places for northern species to go."