ANCHORAGE — A judge has ordered a federal agency to come up with its proposal for providing critical habitat protection for North Pacific right whales, considered the world's most endangered whales.

The decision was issued late Tuesday by U.S. District Judge William Alsup in San Francisco. It orders the National Marine Fisheries Service to come up with its critical habitat proposal for the whales in four months, or explain why not.

Most of the U.S. population of North Pacific right whales summer in one area of Alaska's Bering Sea. There are believed to be fewer than 100 whales.

The judge also said the agency can't call for more study of the issue, but "must use the facts currently available" to come up with its critical habitat proposal.

Alsup described NMFS's behavior regarding the whales as arbitrary and capricious.

Sheela McLean, spokeswoman for the National Oceanic and Atmospheric Administration's fisheries service in Juneau, said the agency is still evaluating the judge's order.

"We will work with the court order," she said.

The ruling was a victory for the Center for Biological Diversity, which filed the lawsuit and petitioned for years for critical habitat designation for the whales.

"The judge here has clearly recognized that right whales are in desperate need of protection. He has ordered the Bush administration to stop dilly-dallying and protect these whales because we simply don't have time to waste to make sure that these whales recover," said Brent Plater, a lawyer for the conservation group.