ALBUQUERQUE Los Alamos National Laboratory, one of the nation's premier nuclear weapons labs, is preparing to lay off hundreds of people because of anticipated federal budget cuts and other factors, lab officials say.

The northern New Mexico lab, where the atomic bomb was born, expects to cut between 500 and 750 positions, said spokesman Kevin Roark. About 12,000 people work at the lab.

The cuts are part of a restructuring plan the lab has submitted to the federal government. If approved, the lab would ask employees to leave voluntarily, with severance packages based on their years of service.

Those who opt for the voluntary buyouts would likely be done working at the lab by January, Roark said. The lab then would reassess whether any employees would be laid off, he said.

Some 700 employees packed an auditorium in Los Alamos on Monday to get an update from lab director Michael Anastasio on the restructuring plan. The rest of the lab's employees watched his address from their offices via closed circuit streaming video.

In a memo to employees, Anastasio said the decision to reduce the work force was a difficult one.

"It directly impacts people's lives, not only those of our employees, but also their families, and the northern New Mexico community. People are the soul of any institution," he said. "You have my personal commitment to make this process as fair as possible."

Sen. Pete Domenici, R-N.M., said the severance package hopefully would encourage those nearing retirement to take it and preserve jobs for those who still have a long future at the lab.

"Nothing about this situation is satisfying," he said. "Faced with ongoing budget uncertainties, LANL's leadership had no choice but to reduce its work force."

Congress has not approved the fiscal year 2008 budget, but Roark notes, "budgets have been flat for the past few years" and the lab has been anticipating a cut.

That and an unusually low turnover rate, which typically stands at 3 percent, are behind the restructuring plan, Roark said.

"The overarching goal is to maintain the long-term viability of the lab," Roark said. "The director is committed to keeping Los Alamos at the forefront of science, keeping Los Alamos as a premier scientific lab in the area of national security. We can't afford to lose that."

Charles Mansfield, president of the Laboratory Retiree Group Inc., said the layoffs could have an impact throughout northern New Mexico.

"It's not just Los Alamos," said Mansfield, who worked at the lab for 17 years before retiring in 1993. "... The lab is a major economic engine for northern New Mexico."

Mansfield described lab workers as "unique," saying any who are displaced would have to travel to Albuquerque for the nearest high-tech jobs.

Greg Mello, executive director of the Los Alamos Study Group, an Albuquerque-based watchdog group, added: "You have to worry about the vulnerable here in New Mexico. We won't have to worry about scientists that have marketable skills. You have to worry about those who don't ... the technicians and construction workers."

Mello contended that layoffs wouldn't be necessary if the lab offered appropriate retirement incentives and reformed what he called "wasteful management practices," including canceling unnecessary construction, reducing subcontractors and cutting back management overhead.

"We need pull money out of nuclear weapons, which are an obsolete form of security and put that money into relevant forms of security that are needed in our communities, especially energy security," he said. "If we cling to the labs against the current of history, then were going to be left behind."

Los Alamos is not the only national lab preparing to trim its work force.

Lawrence Livermore National Laboratory in California announced last week that it plans to cut about 500 jobs because of rising costs stemming from a changeover in management and potential federal budget cuts.

Sandia National Laboratories in Albuquerque released its work force restructuring plan last month, but spokesman Michael Padilla has said the lab hasn't made any decisions regarding layoffs.

Los Alamos and Sandia currently are funded at fiscal year 2007 levels under a continuing resolution that expires next month. Meanwhile, lawmakers are trying to reach agreement on an appropriations package that would fund the federal government for the remainder of the 2008 fiscal year.