Mayor Marion Barry, under pressure to relieve crowding in the District's prisons, is expected to invoke emergency legislation today that will allow the city to begin the early parole of certain inmates during the next few days, Barry administration officials said last night.

Barry's action would permit the District to shorten by 90 days the sentences of some inmates convicted of nonviolent crimes, making them eligible for parole almost immediately -- provided that D.C. corrections officials certify that the inmate population has remained above the prison system's official capacity for 30 consecutive days and that an emergency exists.

Under the law, requested by Barry and signed last week, the eligible inmates must appear before the Parole Board for hearings.

City Administrator Thomas M. Downs met yesterday with D.C. Corrections Director Hallem H. Williams Jr. and Parole Board member Bernice Just in an apparent attempt to prepare for Barry's action, sources said.

According to D.C. government statistics, 1,970 prisoners are housed in the city's three Occoquan prisons at Lorton Reformatory -- 689 more than the number permitted under an order by U.S. District Judge June L. Green.

The city's inmate population is growing by about 200 a month, largely because of an eight-month police crackdown on drugs, according to Peter Nickles, the lead attorney for Lorton inmates in lawsuits against the District.

Green, who granted a second one-month reprieve this week from her court order on the Occoquan prisons, warned District officials that they must act immediately to reduce inmate populations there.

"Obviously, we are now at a crisis situation," Green said during a hearing Tuesday on recommendations by former D.C. Superior Court judge John D. Fauntleroy Jr., whom Green appointed to develop a plan to reduce crowding at five Lorton prisons.

Federal law enforcement officials speculated last night that Barry would invoke the emergency law today, at the start of the holiday weekend, in an effort to meet a July 13 deadline for a detailed report on the number of inmates eligible for release under the measure.

Barry has said the measure would allow for the early release of more than 250 inmates within 180 days.

Rep. Stan Parris (R-Va.), a longtime critic of the District's management of the Lorton complex in Fairfax County, introduced a bill Tuesday to repeal the emergency measure, saying the city's plans for the early release of hundreds of inmates would pose a serious threat to public safety.

District officials emphasize that inmates who were convicted of violent crimes -- including homicide, rape, assault with a dangerous weapon and armed robbery -- and those serving mandatory sentences on drug convictions would not qualify for early parole.

Corrections officials have said that most inmates paroled under the measure would be released only 30 days early.Staff writer Tom Sherwood contributed to this report.