BOISE, Idaho - The U.S. Fish and Wildlife Service has asked a federal judge to allow it to withdraw from a recent agreement concerning a timeline for deciding whether sage grouse should be listed as an endangered species across much of the Rocky Mountain West.

The agency, in documents filed in U.S. District Court here, said it "inadvertently" entered into the agreement without proper review, and that the agreement could delay its decision about whether the chicken-sized grouse deserves federal protection.

Such a declaration could lead to new restrictions on residential, oil and gas and agricultural development in Wyoming and the West.

Laird Lucas, a lawyer representing the environmental group Western Watersheds Project, said the group would file a brief arguing against the agency's request.

He said Fish and Wildlife was attempting to get out of last month's agreement so that it could make a decision on the sage grouse listing ahead of the agreed-upon timetable so as to avoid a report by the Western Association of Fish and Wildlife Agencies.

The report, called the Conservation Assessment of Greater Sage-Grouse and Sagebrush Habitats, is scheduled for publication in November.

"If we don't wait for that, it means they can put science aside," Lucas said. "We've already seen them do it."

After the Bush administration decided not to list the bird in 2005, the Western Watersheds Project sued Fish and Wildlife.

In December, U.S. District Judge B. Lynn Winmill issued a decision highly critical of the agency's decision, saying the service failed to use the "best science" available when deciding not to give the declining species protection under the federal Endangered Species Act.

As part of the remedy phase of the lawsuit, the agency and the Western Watersheds Project worked out an agreement, called a "stipulation of remand," that set a timetable for various actions, with a final decision to be made by the agency in May 2009.

In the documents filed last week seeking to get out of the agreement, the agency said it "could, and possibly may, issue a new 12-month finding by Dec. 4."

Lucas said issuing a decision on sage grouse in December would exclude the November report because the agency wouldn't have enough time to include it.

"We anticipate that the report will show a very bleak situation," Lucas said. "We've had millions of acres burn up in the last few years in the West. We've had West Nile virus, and we've had energy development through much of the best remaining sage grouse habitat. On top of that, we have global warming. We think this report will be dire and show sage grouse need to be protected under the Endangered Species Act."

Lucas said the agency was playing politics in its attempt to get out of the agreement.

"I think what happened is the political folks realized their hands would be tied and they wanted out," he said.

The sage grouse population has been declining for decades, and the bird now occupies about half of its original, year-round habitat. In January 2005, the Fish and Wildlife Service estimated there were between 100,000 and 500,000 greater sage grouse.

The birds are found on the sagebrush plains of 11 states - from Colorado to California and north to the Canadian border.