All convicted criminals sentenced to prison terms in D.C. courts beginning next week would be housed in federal corrections facilities indefinitely under a proposal offered yesterday by the U.S. Justice Department to reduce crowding gradually at the city's jail, a spokeswoman for Mayor Marion Barry said.

District officials said, however, that even with the offer of federal assistance to make room for inmates, the city will be unable to comply with a federal judge's order that the jail population be cut by more than 30 percent by Saturday.

After emerging from a meeting yesterday with Deputy U.S. Attorney General D. Lowell Jensen and federal prisons director Norman Carlson, city officials asked U.S. District Court Judge William B. Bryant for a hearing on the proposed jail plan.

Bryant, who has told the city that no new prisoners can be placed in the jail until the city complies with his order, tentatively agreed last night to schedule a hearing on the plan for this afternoon.

The plan, as described by Annette Samuels, the mayor's spokeswoman, would mean that no new inmates would be sent to Lorton Reformatory, the District's prison facility in Fairfax County. Through normal attrition, the number of inmates at Lorton would decline, allowing officials to transfer convicted inmates from the D.C. Jail to Lorton and reduce the D.C. Jail population.

"Because we are not taking convicts in under this plan, if it goes through, we can move people out of D.C. Jail and reduce the number there," Samuels said. "We can't say how long it would take to get the population down. We are trying to take this plan to the court. We're trying to take the whole thing to the judge."

Last month, Bryant ordered the city to reduce the inmate population at the D.C. Jail to a maximum of 1,693, which is about 25 percent above the facility's design capacity. Nearly 2,500 prisoners were being held at the jail yesterday.

Attorneys for the city, who appear to have run out of options with only three days left before Bryant's order is to take effect, are expected to ask the judge to delay implementation of the order or raise the cap on the number of inmates who can be housed at the jail.

The city previously asked Bryant for a delay and a new population ceiling, but until now it has offered no alternative to housing inmates in the city's crowded prison system.

Attorneys representing jail inmates filed papers with Bryant yesterday arguing that the city had delayed remedying crowding long enough and has failed to make "any efforts" to comply with the order.

Justice officials propose taking custody of all felony and misdemeanor criminals who receive sentences beginning Sunday in D.C. Superior Court and U.S. District Court, Samuels said. Justice Department authorities would also take responsibility for housing defendants awaiting trial on federal charges, she said.

Under the plan, sentenced inmates who currently are sent to Lorton presumably could be sent to various federal prisons around the country.

The D.C. Jail was built to house only defendants awaiting trial and those serving sentences for misdemeanors, but it currently holds several hundred sentenced felons who cannot be placed elsewhere. Under the plan, these inmates could be sent to Lorton, where the inmate population also is restricted under federal court orders.

Officials stressed, though, that it is still for Bryant to decide whether the city can continue to place newly arrested defendants at the jail. Law enforcement authorities are concerned that, beginning Saturday, the city might have nowhere to put people arrested for dangerous crimes.

Justice officials and prosecutors in the U.S. attorney's office here declined to comment on the proposal and would only confirm that they met with City Adminstrator Thomas Downs and D.C. Department of Corrections Director James Palmer. "We're cognizant of the public safety problem created by the District's dereliction, and we are offering some aid," said Charles Roistacher, counsel to U.S. Attorney Joseph E. diGenova.