A messenger for a District company that transcribes closed congressional hearings pleaded guilty in federal court here yesterday to a single count of espionage -- with a maximum sentence of 10 years in prison -- in return for the government's promise to drop a more serious charge against him.

Randy Miles Jeffries, 26, pleaded guilty to delivering national defense documents to a person not entitled to receive them. In return, prosecutors agreed to drop another charge, which carries a potential sentence of life in prison, of delivering and attempting to deliver national defense documents to Soviet agents.

U.S. District Court Judge Gerhard A. Gesell did not set a date for sentencing, but he refused to free Jeffries on bond. "It's inconceivable that there would not be some kind of sentence involving jail time," Gesell said. "If he's going to have to serve time, he'd better get started on it."

If Jeffries receives the maximum sentence of 10 years, he would be eligible for parole after serving 3 1/3 years. He could also be fined up to $250,000. U.S. Attorney Joseph E. diGenova said prosecutors would ask "for what the statute provides" at the sentencing hearing.

Jeffries told Gesell that the person to whom he gave the documents was a friend named Kevin Quander. The government contended in its plea document, however, that Jeffries said he had actually passed portions of the documents to the Soviets.

Jeffries, a messenger at Acme Reporting Co., was arrested Dec. 20 at a downtown motel after offering to sell an undercover FBI agent, posing as a Soviet operative named "Vlad," copies of three classified documents for $5,000. One of the documents was a transcript, marked "top secret," of a House Armed Services subcommittee hearing about sensitive military communications programs, prosecutors said.

Jeffries, of 143 Rhode Island Ave. NW, was indicted on the two counts of espionage last week, and was to have been arraigned on the charges yesterday morning. Instead, he entered the guilty plea.

The Jeffries case focused attention on the handling of classified information on Capitol Hill and by private reporting companies after testimony that FBI agents who searched Acme found secret and top secret documents torn into quarters and placed in a large trash barrel. Such documents are supposed to be disposed of by burning or reducing them to pulp.

House General Counsel Steven Ross said yesterday he would recommend that, "to the fullest extent possible," transcribers on the House staff handle all classified hearings and that, if no in-house reporter is available, the outside reporter do the transcription work on the Hill, rather than removing the documents.

The Justice Department has generally taken a hard line in the spate of recent espionage cases. Assistant Attorney General Stephen S. Trott, who heads the Justice Department's criminal division, said the plea arrangement "accurately describes what the man did and exposes him to a sufficient penalty structure so he can pay the price."

He said the harm that might have been done by Jeffries was "absolutely" less than that inflicted by convicted spy Arthur James Walker. Walker, the brother of convicted spy John Anthony Walker Jr., passed to the Soviets two reports classified "confidential," the lowest category of classified information.

Asked why prosecutors agreed to drop the more serious charge against Jeffries, U.S. Attorney diGenova said after the brief court proceeding, "In any espionage case . . . one of the many considerations that go into it are protecting . . . sources and methods."

According to testimony in earlier court hearings in the Jeffries case, a "sensitive source" overheard a series of telephone calls that Jeffries made to the Soviet Military Office at 2552 Belmont Rd. NW, and word-for-word transcripts of parts of the calls were quoted in the plea document filed yesterday.

Intelligence agencies routinely monitor telephone calls to Soviet installations here, but officials are extremely reluctant to disclose the various techniques through which the calls are intercepted or even to acknowledge publicly that such monitoring takes place.

Concern over the strength of the government's case was also a major factor in the decision to accept the plea to the lesser count, sources familiar with the case said. FBI agents arrested Jeffries before he actually delivered any documents to "Vlad." Quander, the friend to whom Jeffries said he gave the documents for safekeeping, destroyed them shortly before Jeffries' arrest because he felt "uneasy about the situation," according to the plea document.

Quander, who according to the plea document drove Jeffries on one of his trips to the Soviet Military Office, received immunity from prosecution in return for testifying before a federal grand jury investigating the case, according to Jeffries' defense lawyer, G. Allen Dale.

Jeffries told the undercover FBI agent that he had already met twice with the Soviets and given them more than 60 "sample pages" of the documents, FBI agent Michael Giglia testified at earlier court hearings.

But Dale said, "We have not backed down from our position that he did not give and did not intend to give documents to the Soviets. We had said all along that yes, he gave the documents to his friend. There really was no defense to that."

According to the plea document by diGenova and Assistant U.S. Attorney Rhonda C. Fields, the top secret hearing transcript involved "discussion of major military system initiatives and procurements, a joint net assessment of the strengths and weaknesses of the United States versus the Soviets in weaponry" and communications, and the security of U.S. military communications.

Donald C. Latham, assistant secretary of defense for command, control, communications and intelligence, who testified at the House hearing, "would have testified in court that disclosure of this information could cause exceptionally grave damage to the United States."