The Federal Bureau of Prisons began a 30-day hiring freeze last week and will have to lay off some of its 35,000 employees next year unless the agency finds other ways to avert a budget crunch, according to Director Harley G. Lappin.

Lappin announced the freeze Friday in a memo to employees and disclosed the prospective layoffs last month in a letter to a federal employee leader. He wrote that it was his "sincere desire" to avoid a layoff -- known as a reduction in force, or RIF -- through other cost-saving measures at the agency, which has a $4.4 billion budget and operates 104 federal prisons.

"However, the reality is that if our continuing efforts are unsuccessful, for whatever reason, the agency will have no choice but to complete a formal reduction in force," Lappin wrote in the June 17 letter to Phil Glover, president of the American Federation of Government Employees Council of Prison Locals.

Layoffs could begin as soon as March and "could affect every employee and position," Lappin wrote. He did not indicate how many workers might be let go.

Judith Garrett, a bureau spokeswoman, said Thursday that neither Lappin nor any other agency official would be available for an interview with The Washington Post. She invited a reporter to submit written questions but had not provided responses by Friday evening.

"It's just a very sensitive area for us to talk about," Garrett said Thursday. "And so we really need to make sure that we're kind of controlling the whole thing to make sure it doesn't go badly."

Glover, whose union represents 20,000 of the agency's workers, said Friday that the bureau has gotten only 91 percent of the funding it requires over the last three years, leading to chronic understaffing. Management has told employees that the agency needs to trim costs by $140 million this year and $300 million in 2005, Glover said.

"You are running short all the time," he said. "It's just not a safe situation."

The prospective layoff could wipe out as many as 2,000 jobs, Glover said. In a memo last month, he urged union members to contact members of Congress to complain about the agency's money woes.

"I cannot stress enough that this is a 'political' problem," Glover wrote. "The Bush administration has chosen not to fund prisons the way they need to be funded." In recent years the bureau has struggled to keep pace with a fast-growing inmate population that has more than tripled since 1990. The agency oversees about 176,000 inmates this year, up from 58,000 in 1990 and 26,000 in 1980, Lappin told a House appropriations subcommittee March 24.

He attributed much of the increase to stricter sentencing guidelines, the abolition of parole and an increase in prosecutions. About 55 percent of inmates entering federal prisons were convicted of drug-related offenses, he said. At the same time, 500 bureau employees have been deployed to Afghanistan and Iraq as part of their military reserve duties, Lappin said.

Inmate assaults against guards and other inmates have increased 28 percent over the last few years, he testified in March.

"The rapid growth of the inmate population and significant crowding have increased the demand on services and facilities," Lappin said. "If not managed properly, this can lead to an increased potential for inmate violence. We must continue to maintain adequate staffing levels and to provide adequate programs and secure our capacity to house the additional inmates."

Lappin said the bureau will "continue to pursue the streamlining, consolidations and other measures to improve the cost efficiency within our operations." Such measures include eliminating some managerial and central office positions, combining some departments, leaving jobs vacant, cutting back food service costs and centralizing prison pharmacy services, according to agency documents obtained by union leaders.

"It looks like rather small cost-cutting efficiencies he's putting in," John Gage, national AFGE president, said in an interview last week.

Last week the Republican-controlled House approved $4.76 billion for the bureau in fiscal 2005 -- $50 million above what the Bush administration asked for. A Senate panel has not yet taken up the bill that funds the bureau.

Bureau of Prisons Director Harley G. Lappin said that although he hopes to avoid a reduction in force, layoffs could begin as soon as March.