The U.S. Fish & Wildlife Service estimates roughly 4,700 polar bears live in Alaska. The worldwide population is believed to be between 20,000 and 25,000. (CBC)

A U.S. federal judge has ordered the Interior Department to decide within 16 days whether polar bears should be listed as a threatened species because of global warming.

U.S. District Judge Claudia Wilken agreed with conservation groups that the department missed a Jan. 9 deadline for a decision.

"Defendants have been in violation of the law requiring them to publish the listing determination for nearly 120 days," the judge, based in Oakland, Calif., wrote in a decision issued late Monday.

"Other than the general complexity of finalizing the rule, defendants offer no specific facts that would justify the delay, much less further delay."

The ruling is a victory for conservation groups that claim U.S. President George W. Bush's administration has delayed a polar bear decision to avoid addressing global warming and avoid roadblocks to development such as the transfer of offshore petroleum leases in the Chukchi Sea off Alaska's northwest coast to oil company bidders.

"We hope that this decision marks the end of the Bush administration's delays and denial so that immediate action may be taken to protect polar bears from extinction," Greenpeace representative Melanie Duchin said in a statement.

A decision to list polar bears due to global warming could trigger a recovery plan with consequences beyond Alaska. Opponents fear it would subject new power plants and other development projects to federal review if they generate greenhouse gasses that add to warming in the Arctic.

Representatives of the U.S. Fish and Wildlife Service did not immediately respond to a call seeking comment Tuesday morning.

Decision should be based on science, says petition author

Kassie Siegel of the Arizona-based Center for Biological Diversity, the lead author of the petition submitted in 2005, called the judge's order a huge victory, despite not knowing whether polar bears ultimately will be listed.

"It means that whatever political interference going on right now is going to be short-circuited," she said.

"The politicians and the bureaucrats in Washington, D.C., are going to have to stop interfering with the decision and get it out the door."

The law requires a decision based on science, she said, and science shows the Arctic is thawing.

"The science is perfectly clear. There's no dispute. The polar bear is an endangered species," she said.

Last week, a federal committee studying the polar bear's status in Canada assessed it as a species "of special concern" — the same status it has had since 1991. The designation is two steps down from "endangered" and one down from "threatened."