Three New Mexico sheep ranchers have sparked a debate within the Interior Department that some are concerned could set a precedent for wildlife management throughout the entire park system.

Based on the ranchers' complaints that they have suffered heavy sheep losses to mountain lions, G. Ray Arnett, assistant secretary of the interior for fish and wildlife and parks, is pushing to allow them to shoot the lions in Carlsbad Caverns and Guadalupe Mountains national parks.

The ranchers claim to have lost nearly 1,000 sheep in the past two years to lions protected within the two parks along the New Mexico-Texas border. Arnett intervened in the dispute at the request of William Huey, director of New Mexico's natural resources department and an old friend from Arnett's days as director of California's state game department. Arnett's proposal would allow New Mexico game wardens, accompanied by park rangers, to pursue lions into the parks and shoot those believed to be killing sheep.

Environmentalists and veteran National Park Service officials warned that the break with longstanding park policies could set a dangerous precedent for parks elsewhere. Attorneys for the Sierra Club and Defenders of Wildlife have filed suit in U.S. district court in Albuquerque to try to block the move.

Brandt Calkin, the Sierra Club's Southwest representative, argued that allowing lions to be killed in the remote parks would be an ill-conceived public subsidy for an area that is clearly not prime sheep country. Though the ranchers disagreed, Calkin suggested that using guard dogs or shepherds to protect the sheep would be a better solution to the problem. "Sheep are everywhere," Calkin said. "Mountain lions are not."

"I think it would be very tragic for our park philosophy to shift away from the protection of wildlife," said William Dunmire, superintendent for the two parks. Dunmire is charged with drafting a formal agreement with New Mexico to mirror Arnett's proposal.

Animals have been killed occasionally within national parks. For example, some grizzly bears in Yellowstone were killed after they began invading park campgrounds. But Arnett's critics say his request for an agreement delegating that responsibility to nonpark personnel is a dangerous new step.

"What really worries me is that the more we go in and manipulate the parks for interest outside the parks, the more we're going to lose the naturalness and vigor of that system," said Laura Loomis of the National Parks and Conservation Association.

But in an Aug. 29 letter to a concerned Maine citizen, Arnett said no policies would be changed until environmental consequences were assessed and several alternatives considered. Any decision, he said, "will be based on careful consideration."

Dunmire said park superintendents around the country are watching to see what happens in the case. "There are a lot of parks with similar questions," he said. "This will be a precedent for the national parks system. Some folks higher up have said it wouldn't be. My opinion is that it would be."

With that in mind, Dunmire has drafted an agreement that would allow New Mexico officials to kill lions inside the park only if they have a "hot scent" -- that is, a fresh trail, no more than 24 hours old, leading into the park from a dead sheep. The state would have to get approval from the park service in advance each time it sent one of its trappers across the park boundary.

Interior solicitors have been scrutinizing the proposed agreement since April, but have not yet sent it to New Mexico officials for their approval. Park service rules require the agency to solicit public comments on the proposed agreement before signing it.

Given that park officials do not even know how many lions live in the parks and the surrounding area, Dunmire said he would have liked to delay the agreement for two years until a study of the lion population in the park is completed. But he said the clamor for the agreement forced him to act sooner.

The park service's cautious approach frustrates the ranchers, who say they need immediate relief. Marion Hughes said he lost 500 sheep worth $26,000 last year to lions -- a record in the 53 years he has worked in the area. "If they had given me permission to have gone in there and taken the lion or two doing most of the killings, I could have salvaged it," he said. "Now it's like crossing a penitentiary fence to go into the park as far as hunting."

His complaints are echoed by ranching neighbors Curtis Doyle and David Kincaid. The ranches of all three men sit on a great plateau along the northern edge of the two national parks. Sheepmen call the cactus-studded landscape "five-by- sixty country" -- an old joke that only sheep with mouths five miles wide running 60 miles an hour can find enough forage to survive.

The harsh conditions have forced everyone in the area out of the sheep business except Hughes, Doyle and Kincaid. Doyle said his continuing sheep losses to the lions may bankrupt him. He accused the park service of stalling in hopes that the Sierra Club suit will overturn Arnett's plan before it can be put into practice.

"They're using all this red tape. We can't go on like this forever and they know it," Doyle said.

But Hughes said he has no intention of abandoning his fight with the park service. "I'm going to stay here and battle them until I die or starve."