Environmental groups on Thursday accused US President Barack Obama's administration of failing to ensure the survival of polar bears after it stopped short of listing the animals as endangered.

Kassie Siegel of the Center for Biological Diversity, who has led legal efforts to protect the polar bear, said that the Obama administration "sacrificed sound science for political expediency."

"The Obama administration delivered a lump of coal to the polar bear for Christmas," she said in a statement.

The US Fish and Wildlife Service, responding to a legal suit, agreed Wednesday that climate change posed "serious threats" to the polar bears by melting their Arctic habitat in the northernmost state of Alaska.

But the service said the threat was "in the foreseeable future" and that polar bears were not "in danger of extinction." A listing as endangered would likely lead to federal protection of areas rich in oil and gas.

Andrew Wetzler of the Natural Resources Defense Council questioned the administration's logic, saying: "I guess if a wrecking ball is barreling down on your house, you are just 'threatened.'"

The decision left in place a 2008 ruling under president George W. Bush, whose administration was much less eager than predecessors to protect animals under the Endangered Species Act.

The Obama administration has pledged to become more active in fighting climate change, and it incurred the wrath of the oil industry on Thursday by announcing it would regulate greenhouse gas emissions by power plants.

Last month, the Fish and Wildlife Service set aside 187,000 square miles (484,000 square kilometers) off Alaska's northern shore as a bear habitat, which means any project that could impact the animals' way of life must undergo careful review.

The northern polar cap has shrunk between 15 and 20 percent over the last 30 years. But a recent study in the British journal Nature said that the melting was not inevitable and could be reversed.