"We believe that the ... decision to list the polar bear was not based on the best scientific and commercial data available," Alaska Gov. Sarah Palin said in a statement.

Polar bears live only in the Arctic and depend on sea ice as a platform for hunting seals. The US Geological Survey reported last year that two-thirds of the world's polar bears -- some 16,000 -- could be gone by 2050 if predictions about melting sea ice hold true.

In putting the white bears on the threatened list, Interior Secretary Dirk Kempthorne acknowledged that human-caused greenhouse gas emissions contributed to the planetary warming that has damaged the polar bears' habitat.

However, the decision does nothing to address climate change, and Kempthorne said any real solution to that underlying problem is up to the world's economies.

"BIDDING OF OIL COMPANIES"

The Interior Department does not comment on pending litigation and had no statement on the Alaska suit.

Alaska's suit contends that the US Fish and Wildlife Service -- part of the Interior Department and the agency that helped make the polar bear decision -- failed to consider that polar bears have survived through previous warming periods.

Environmental groups vowed to seek to have the lawsuit dismissed.

"The state's lawsuit isn't about the science of global warming and polar bears," said Melanie Duchin of Greenpeace USA. "It is merely doing the bidding of oil companies that want to drill for oil in sensitive polar bear habitat, without any concern for how that oil will impact the climate when it's burned."

Alaska maintains that the polar bear population has doubled to as many as 25,000 over the last 40 years as a result of current regulations and conservation programs in Alaska and internationally.

"Additional regulation of the species and its habitat under the Endangered Species Act will deter activities such as commercial fisheries, oil and gas exploration and development, transportation and tourism within and off-shore of Alaska," the lawsuit said.

Greenpeace, the Natural Resources Defense Council and the Center for Biological Diversity are seeking to intervene in the case.

(Editing by Sandra Maler)