The administration, as part of its budget-cutting drive, is halving a program that the federal prison director believes is helping to prevent released convicts from committing more crimes: halfway houses.

In his anticrime speech Monday, President Reagan urged several legal and administrative steps to crack down on offenders but pledged no new federal money for the effort.

Now it appears that funds for at least one anticrime program will be drastically cut. The Federal Bureau of Prisons, part of the Justice Department, will slash $13 million from its budget by curtailing the use of 400 halfway houses in communities throughout the nation.

Bureau Director Norman A. Carlson disclosed the cut in a conversation in his office Wednesday with 12 visiting convicts. Carlson told them he acted only because administration budget cutters ordered him to trim $24.5 million from his $383.8 million budget.

"We hate to do it," he said. "Unfortunately, we have to cut." Carlson told the convicts that before he was ordered to make the cuts he had planned to expand greatly the use of halfway houses.

Operated by local governments or private groups, the houses are a way station for convicts during the weeks immediately before their release on parole. Last year, under contract with the operators, the bureau sent about 9,000 convicts to halfway houses for an average of 80 days each.

The budget cut means that the average period will be cut to 45 days. Carlson said he had hoped to extend it to 120 days.

The cut could be "an additional cause of crime" because it will give convicts less time to find steady jobs before being freed, said Edward I. Koren, a lawyer with the national prison project of the American Civil Liberties Union.

"That period of time is crucial in getting someone to lead a law-abiding life," Koren said. "They set up a guy with a stable source of income and a place to live, and he gets to be involved in the community again . . . . "

Carlson stopped short of predicting that the cut would cause more crime, but he told the visiting convicts, "Research indicates an average of 60 days is enough . . . . Research shows if a guy wants to make it, he can do it. It's harder, no question about it, particularly with the employment market the way it is."

In an interview, Carlson said that although he does not like the cut, "It's not going to have disastrous effects."

Ironically, the cost of keeping a federal prisoner in a halfway house is less than in a prison--$26.85 vs. $34.40 a day. But Carlson said he cannot close any of his 41 prisons because they already house 26,300 convicts, 2,650 more than they were designed for.

Keeping large numbers of prisoners behind walls for an average of an additional 35 days each as part of the cut will add more than 800 persons to the already overcrowded daily prison count.

State prisons also are overcrowded, with about 300,000 prisoners, but in his speech Reagan did not mention a major recommendation of his administration's outside task force on violent crime--$2 billion in federal aid to help build more state prisons.

Carlson told the visiting convicts that he was sharply cutting other items, such as travel, in his budget. He reassured them that money for food and medical care in the federal prisons would not be cut.

The use of halfway houses as a correctional tool has been controversial because of publicized episodes about new crimes committed by their residents. The concept of such a rehabilitative tool grows out of a body of social theory that Reagan criticized in his speech as "utopian presumptions about human nature."

The convicts who visited Carlson are from federal prisons throughout the country. They are in Washington for a series of seminars sponsored by Charles Colson's Prison Fellowship, a born-again Christian organization founded by the former Watergate conspirator to promote prison reform.