BOISE, Idaho - A federal judge is holding the U.S. Fish and Wildlife Service to a deal reached with environmentalists that sets a timeline and other conditions on whether to grant threatened or endangered status to the sage grouse.

The wildlife agency sought to back out of a stipulation filed with the court in January that set a May 2009 deadline to determine whether to list the bird under the Endangered Species Act. The deal also required the agency to consider a new and critical scientific report on the bird due out in November and give the public 60 days to comment on the report's findings.

Across Wyoming and the West, decisions about the sage grouse are considered critical to the future of gas and oil drilling, agriculture and urban growth.

Last month, government attorneys sought to back out of the deal, saying top Fish and Wildlife officials never signed off on it. The agreement was approved by Department of Justice lawyers, who negotiated the timeline and other details with the Idaho-based Western Watersheds Project.

In U.S. District Court Friday, Robert Williams, the Justice Department lawyer representing the wildlife service, said the agreement is technically not binding because the government opted to back out before the judge signed it.

Williams also said that holding to arbitrary deadlines would keep agency officials from making a listing decision before 2009, and he argued that it's customary for agency heads to consent to agreements before steps are taken to make them legally binding.

"Unfortunately, that didn't happen here," Williams said.

Judge B. Lynn Winmill rejected those claims, saying the deal, which was filed with the court, should be treated and honored like any other legally binding contract.

The ruling is another setback for the agency since it ruled in January 2005 that the sage grouse did not merit threatened or endangered status.

In 2006, Western Watersheds Project and other groups challenged the agency's decision in federal court, claiming the decision not to list the species was flawed and unfairly influenced by political agendas.

In December, Winmill scolded the service for failing to use the best available science in its decision to deny listing.

He also harshly criticized what he said was the "inexcusable conduct" of former Deputy Assistant Interior Secretary Julie MacDonald, who had oversight of the agency. MacDonald, who resigned last year, intimidated agency staffers, edited scientific conclusions and otherwise intervened in the listing process "to ensure that the 'best science' supported a decision not to list the species," Winmill said.

Environmentalists and wildlife managers say the bird's population and habitat have been diminishing for decades due to wildfires, grazing, energy development and drought. Researchers say the bird now occupies about half of its original, year-round habitat, which stretches across 11 Western states from California to Colorado and North Dakota.

Population estimates vary, but more exact numbers and other fresh, critical data on sage grouse will be included in the comprehensive study due in November by the Western Association of Fish and Wildlife Agencies, an organization representing 23 states and Canadian provinces stretching from Alaska to Texas.

The Fish and Wildlife Service announced this week that it was conducting a new review of the bird's status.

Laird Lucas, attorney for Western Watersheds Project, called Winmill's ruling a victory for science over politics.

The wildlife agency said "it wanted discretion to make a decision by the end of 2008, and everybody knows that's the last full month in office for the Bush administration," Lucas said. "Let's just leave aside politics. The science is what needs to drive this decision."