Reagan administration officials told a congressional committee yesterday that they will fire 653 employes and end several programs at St. Elizabeths Hospital unless a $25 million gap in next year's budget is filled.

The officials' reiteration of previously reported plans to fire 16 percent of the hospital's 2,900 employes was made shortly after D.C. Del. Walter Fauntroy said in a separate hearing that federal officials "have no intention to fire people."

Fauntroy said he had been told that the Department of Health and Human Services was only "examining options" on where the mental hospital should cut back if neither the District nor Congress appropriated more money. But Robert Trachtenburg, deputy director of the federal agency in charge of the hospital, said the firings must occur by Dec. 1 if no extra money is found. "The issues are the same," Trachtenburg said. "It's still a budget problem."

Representatives of the District's budget office and the congressional committees working on the city's appropriations would not promise yesterday to make up the $25 million, but Fauntroy said he is "confident" that Congress will "forbear for one year while a plan working out the transfer" of the hospital to city responsibility is developed.

The federal government has tried for two decades to give the hospital--90 percent of whose patients are city residents--to the District. The latest stage in that effort is the hospital's plan, ordered by the federal government, to fire 653 employes and cut several programs if more money isn't found to supplement its $118 million budget for the year beginning Oct. 1.

Under a draft of the cost-cutting plan, the hospital would, among other measures, drop its newly signed $3.4 million contract with D.C. General Hospital, which cares for 25 physically ill patients daily; fire 195 employes from its own unit that cares for the physically ill; fire 100 housekeeping, dietary and laundry workers; drop its plan to replace its "antiquated" telephone system and drop a contract to improve its billing procedures.

Robert Johnson, director of D.C. General, said in an interview that the plan is "ridiculous" because it assumes all of the physically ill patients at St. Elizabeths would be treated at D.C. General with no extra money involved.

Mary Horn, president of Local 2095 of the American Federation of State, County and Muncipal Employees, which represents more than 2,000 employes at St. Elizabeths, also attacked the proposed reductions. "No one's given a lot of thought to the fate of the patients," she said. "It's just take the knife and let's cut it apart with too quick, haphazard planning."

The cost-cutting plan "doesn't mean we're going to take them patients to the gate and drop them off," said Dr. William Mayer, administrator of the Alcohol, Drug Abuse and Mental Health Administration, the federal agency with responsibility for St. Elizabeths. "We feel morally bound to take care of the patients who are there."

But Mayer told the committee yesterday that the hospital is "inordinately" large in light of its decreasing number of residents, and he recommended the closing of its physical care department and its training programs in psychiatry, psychology, nursing, social work and chaplaincy. "I'm not here to ask Congress for more money," he said, noting that the hospital serves "almost exclusively a local population."

Under questioning from Sen. Arlen Specter (R-Pa.), Mayer said programs for drug addicts and alcoholics could be closed and those patients transferred to city-run programs.

After the hearing, Specter said Dr. Mayer had not given him the specific information Congress needs about such transfers. "He did say they drug addicts would be ousted without a source of care," Specter said. "I'm seriously concerned about what's going to happen to drug abusers turned loose on the streets, if they turn to robbing and burglarizing."

Gladys Mack, director of the city's Office of Policy and Program Evaluation, said the hospital cannot be compared with state mental hospitals because the presence of the federal government in the District attracts a large number of psychotic, homeless people "seeking elected officials they want to contact." She further noted the hospital is used for special federal purposes, such as U.S. Immigration and Naturalization Service officials' recent lease of space from St. Elizabeths to house Cuban refugees who are being detained.

In the absence of a commitment from either District or congressional officials of more financial support for the hospital, the D.C. Mental Health Association asked that HHS Secretary Margaret Heckler override the cost-cutting measures.

"Last week, when Secretary Caspar Weinberger learned the Defense Department planned to shoot dogs, he ordered the plan dropped," said Lillian Secundy, president of the association. "Now the Department of Health and Human Services is planning to shoot a hospital--St. Elizabeths--and we at the Mental Health Association are hoping that Secretary Margaret Heckler will act as humanely as Secretary Weinberger."