The U.S. Court of Appeals delayed last night the implementation of an order that would have prohibited any new prisoners sentenced in D.C. Superior Court after today from being sent to the District's Lorton Reformatory.

The appeals court issued an administrative stay about an hour after the federal government filed papers asking for an emergency stay and summary reversal of U.S. District Judge June L. Green's order, issued Friday.

"Plainly, this is judicial overreaching in its most pristine form" and an "abuse of discretion," the federal government said in its papers.

Green's order was expected to cause 300 to 500 D.C. prisoners each month to be sent to federal prisons, which are already 56 percent above capacity, lawyers for the federal government argued in their papers.

The appeals court also ordered the D.C. government and attorneys for inmates at Lorton's Central facility to file replies to the federal government's motions by 10 a.m. Thursday. The court did not set a hearing, but said the stay would remain in effect until further order.

"I can't say it was a surprise, but obviously we're disappointed," said D.C. Corporation Counsel Frederick D. Cooke Jr. "We will file our papers later this week as the court has asked us to do.

"We haven't been brought to a screeching halt by this," Cooke said. He said the city was continuing to give early releases to some inmates convicted of nonviolent crimes and negotiating with inmates' attorneys to ease prison population limits.

Edward R. Sargent, a Corrections Department spokesman, said the delay "would not put too much of a strain on the system," but he added, "in the long term it would be devastating if the appeals court doesn't uphold Judge Green's decision."

Attorneys for the Central inmates could not be reached for comment.

Retired D.C. Superior Court judge John D. Fauntleroy Jr., who is Green's special court officer concerning prison crowding, said last night that "everything depends on whether the Court of Appeals" will issue a longer stay.

Green's order came in the seven-year-old lawsuit brought by inmates at the Central facility, which for the last month has exceeded its court-ordered population ceiling. The latest population figures, for Friday, showed the prison housing 1,235 inmates compared with the ceiling of 1,166.

Last week Green held the city in contempt for exceeding the inmate ceiling and imposed a $250-a-day fine for each Central dormitory that remains in violation of the ceiling.

In addition, the city is under court order to reduce the number of inmates at the three Occoquan facilities by 100 before the end of the month and ultimately to meet an inmate ceiling of 1,281. On Friday, a total of 1,952 inmates were in the Occoquan prisons.

Green's order applies to all prisoners receiving new sentences in D.C. Superior Court, except those with other cases pending and those sentenced under the Youth Act or to work-release programs.

The government's arguments, which are mostly the ones made Thursday during a two-hour hearing before Green, center on the judge's decision to add Attorney General Edwin Meese III as a defendant in the suit by Central inmates.

In doing so, Green reversed her own order of December 1980 dismissing the attorney general from the suit. At the time of her dismissal, neither the city nor the inmates appealed the dismissal.

The government argued that Meese cannot be added to the suit and required to adhere to the settlement negotiated five years ago between the city and the inmates.

"The District Court's attempt to find a 'quick fix' to the overcrowded D.C. prison system by inflicting that problem on the federal prison system is undoubtedly the result of years of frustration with the District in this and several related cases," the government said in its papers, which were signed by U.S. Attorney Joseph E. diGenova and Assistant U.S. Attorney Royce C. Lamberth, who has been Meese's main representative on the prison question.

"Nonetheless, it is entirely unsupportable and represents a clear case of judicial overreaching," the government's papers stated.

The government also argued that even if Green had the authority to add Meese to the suit, she could order a remedy that would address crowding only at Central, not the entire prison system. Green also presides over cases addressing crowding at Lorton's Maximum and Occoquan prisons.

"The separate suits . . . each deal with a specific facility, and any relief ordered in each case must be confined to that part of the District's prison system," the papers said.