By Deborah Zabarenko, Environment Correspondent

WASHINGTON, Jan 7 (Reuters) - A U.S. decision on whether global warming threatens polar bears will be delayed as much as a month, the federal Fish and Wildlife Service said on Monday, prompting ire from environmental groups.

The deadline for deciding whether to list the big white bears as threatened under the Endangered Species Act is Wednesday but a government statement said analysis of scientific data and public comment will take more time.

"We expect to provide a final recommendation to the Secretary of the Interior and finalize the decision within the next month," the statement said.

A key piece of data under consideration is a September report from the U.S. Geological Survey that predicted polar bears could disappear from places where Arctic sea ice is melting fastest, including the northern coast of Alaska.

Two-thirds of the world's polar bears could be gone by 2050 if predictions about melting sea ice hold true, the report said. The ice is melting at least in part because of human-caused climate change, scientists have said.

Polar bears depend on sea ice as a platform for hunting seals, and without it, the bears could be forced onto land, where they are inefficient hunters.

Within minutes of the government's announcement of the delay, environmental groups vowed to sue to enforce the deadline in the polar bear case.

"The Bush administration has squandered seven years denying the devastating scientific evidence of global warming," Kert Davies of Greenpeace USA said in a statement. "Stalling has cost us dearly, putting the polar bear at risk of extinction and jeopardizing the future welfare of billions of people around the world."

Greenpeace, the Natural Resources Defense Council and the Center for Biological Diversity said in a joint statement they plan to start the legal process on Wednesday with a formal notice to sue, as required under the Endangered Species Act.

(Editing by Sandra Maler)

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