Conservation groups served notice on Friday that they would file suit accusing the federal government of failing to protect leatherback sea turtles along the U.S. West Coast as required under the Endangered Species Act.

The three groups said the National Marine Fisheries Service, a U.S. Commerce Department agency, missed a January 5 deadline for designating Pacific habitat critical to the survival of leatherbacks, listed as an endangered species since 1970.

The notice of intent gives the agency 60 days to resolve the situation before a lawsuit is filed in federal court.

Leatherbacks, which can grow to more than 6 feet in length and weigh nearly 200 pounds, are believed to number in the thousands throughout the entire Pacific, with the biggest human threats to them posed by commercial fishing operations.

"They are the largest, deepest-diving sea turtles left on the planet," said Chris Pincetich, a marine biologist at the Turtle Island Restoration Network.

"They've survived the extinction of the dinosaurs, but ... they may have as little as 10 years left."

Joining his group in threatening legal action were the Center for Biological Diversity and the conservation group Oceana.

The Fisheries Service last year proposed designating 70,000 square miles of ocean off the coast of California, Oregon and Washington state as critical habitat for leatherbacks that migrate there from Indonesian nesting grounds to feed on jelly fish. But those regulations have yet to be finalized.

The proposed rules would require any changes in fishery management or approval of other commercial activities in the habitat area to take the well-being of the turtles into consideration.

In 1992, the government took what was regarded as a major step toward safeguarding all sea turtles when it began requiring shrimp trawling nets to be equipped with special devices that help prevent turtles from being swept up.

Jim Milbury, a spokesman for the Fisheries Service, declined to comment on the legal action by the three groups.

The groups said some 2,100 adult female leatherbacks are believed to inhabit the entire Pacific, but a precise estimate for males is impossible to come by, because they spend their entire lifetime at sea. Females can only be counted when they crawl onto beaches to lay their eggs, Pincetich said.

Determining a sustainable population target is difficult, he said, but environmentalists would eventually like to see them number in the millions in the Pacific.