WASHINGTON - The Interior Department declared the polar bear a threatened species yesterday because of the loss of Arctic sea ice but also cautioned the decision should not be viewed as a path to address global warming.

Interior Secretary Dirk Kempthorne cited dramatic declines in sea ice over the last three decades and projections of continued losses, meaning, he said, that the polar bear is a species likely to be in danger of extinction in the near future.

But Kempthorne said it would be "wholly inappropriate" to use the protection of the bear to reduce greenhouse gases, or to broadly address climate change.

The Endangered Species Act "is not the right tool to set U.S. climate policy," said Kempthorne, reflecting a view recently expressed by President Bush.

The department outlined a set of administrative actions and limits to how it planned to protect the bear with its new status so that it would not have wide-ranging adverse impact on economic activities from building power plants to oil and gas exploration.

"This listing will not stop global climate change or prevent any sea ice from melting," said Kempthorne. He said he had consulted with the White House on the decision, but "at no time was there ever a suggestion that this was not my decision."

Kempthorne, at a news conference, was armed with slides and charts showing the dramatic decline in sea ice over the last 30 years and projections that the melting of ice - a key habitat for the bear - would continue and may even quicken.

He cited conclusions by department scientists that sea ice loss will likely result in two-thirds of the polar bears disappearing by mid-century. The bear population across the Arctic from Alaska to Greenland doubled from about 12,000 to 25,000 since 1960, but he noted that scientists now predict a significant population decline.

Studies last year by the U.S. Geological Survey suggested 15,000 bears would be lost in coming decades with those in the western Hudson Bay area of Alaska and Canada under the greatest stress.

Kempthorne said that it is melting sea ice and not subsistence hunting and energy development that poses the threat to polar bears. While some subsistence hunting by Alaska natives is allowed, the United States bans hunting bears for sport.

Canada allows limited sports hunting of bears. The Hudson Bay bear population off Canada has decined by 22 percent in the last 20 years, according to one study.

But when asked how the bear will be afforded greater protection, Dale Hall, director of the U.S. Fish and Wildlife Service, had difficulty coming up with examples.

Better management of bear habitat on shore and making sure bears aren't threatened by people including hunters, more studies on bear population trends and their feeding habits were among the areas mentioned. "I don't want to prejudge recommendations for [bear] management," said Hall whose agency administers the Endangered Species Act.

Environmentalists were already mapping out plans to file lawsuits challenging the restrictive measures outlined by Kempthorne.

"They're trying to make this a threatened listing in name only with no change in today's impacts and that's not going to fly," said Jamie Rappaport Clark of Defenders of Wildlife and a former U.S. Fish and Wildlife Service director.

Members of Congress also were skeptical.

The Bush administration "is forcing the polar bear to sink or swim," said Rep. Edward Markey (D., Mass.), chairman of a House committee on global warming.

Sen. John Kerry (D., Mass.), called it "a lifeline for our last remaining polar bears" but said the bear's survival won't be assured without limits on oil development in the same Arctic waters where the bears are found.

Despite the new listing, the announcement underscores the need to approve climate legislation that would limit the release of greenhouse gases and avert the future effects on climate change, said Sen. Barbara Boxer (D.,-Calif.), chairwoman of the Environment Committee.

Scientists have blamed global warming for the disappearance of sea ice which is vital for the bear's survival.

Summer ice surrounding the North Pole declined an average of 10 percent per decade since 1979, with a loss of about 28,000 square miles per year, according to the National Snow and Ice Data Center. Last year was the sharpest drop, as the amount of sea ice in September fell to 1.65 million square miles, or 23 percent below the previous low in 2005.

Kempthorne proposed 15 months ago to investigate whether the polar bear should be declared threatened under the Endangered Species Act. That triggered a year of studies into the threats facing the bear and its survival prospects.

A decision had been expected early this year, but the Interior Department said it needed more time to work out many of the details, prompting criticism from members of Congress and environmentalists. Environmentalists filed a lawsuit aimed at forcing a decision and a federal court on April 29 set a May 15 deadline for a decision.

A species is declared "threatened" under the Endangered Species Act if it is found to be at risk of becoming endangered in the foreseeable future. If it does not make progress toward recovery, it can be declared "endangered" meaning it is at risk of extinction and needs even greater protection.