Kempthorne said he is accepting the recommendation of U.S. Fish and Wildlife Service Director Dale Hall to list the polar bear under the Endangered Species Act.

Officials said scientific evidence shows the ongoing loss of sea ice threatens, and will likely continue to threaten, polar bear habitat. The loss of habitat, officials said, puts polar bears at risk of becoming endangered in the foreseeable future, the standard established for designating a threatened species.

"I am also announcing that this listing decision will be accompanied by administrative guidance and a rule that defines the scope of impact my decision will have, in order to protect the polar bear while limiting the unintended harm to the society and economy of the United States," Kempthorne said.

He said his decision was based on three findings.

"First, sea ice is vital to polar bear survival. Second, the polar bear's sea-ice habitat has dramatically melted in recent decades. Third, computer models suggest sea ice is likely to further recede in the future."