Accused spy Ronald W. Pelton admitted at his espionage trial today that he told Soviet agents about a secret U.S. operation to intercept Soviet communications, but he minimized the damage caused by this disclosure and denied telling the Soviets about three other secret U.S. intelligence projects he is charged with compromising.

Pelton, who was on the stand for four hours today and will return Tuesday, admitted that he made incriminating statements to FBI agents in November about his alleged espionage contacts with the Soviets. But he denied giving them any information about U.S. code-breaking capabilities. Pelton, a former National Security Agency employe, also said he did not comply with Soviet demands for information about U.S. spy satellites and NSA projects to monitor communications at Soviet embassies around the world.

Responding to questions from his court-appointed attorney, Fred Warren Bennett, Pelton testified that the most sensitive classified information he admitted disclosing to the Soviets related to an intelligence-gathering operation that is being referred to in court as Project A.

Project A has been described by government witnesses as an NSA program to intercept Soviet communications using a specific kind of equipment. Sources have told The Washington Post that the interception operation involved U.S. submarines in the Sea of Okhotsk, between the Kamchatka Peninsula and the eastern Soviet mainland.

Pelton testified that he told FBI agents that he believed that the Soviets had already known about Project A because of an incident that occurred a few years before he left the agency in 1979. He testified today that he discussed this episode in detail with FBI agents during an interrogation session shortly before he was arrested in November.

The incident that Pelton was referring to appears to be what one knowledgeable source described as a collision between a U.S. submarine and a Soviet submarine in the Sea of Okhotsk. The Soviet submarine surfaced and radioed for help, while the American submarine slipped away, one knowledgeable source said.

The collision, like many classified details in the Pelton case, has not been referred to in open court.

In recounting how he described the incident to FBI agents, Pelton said, "I felt the Soviets were aware of Project A but couldn't do anything about it."

During his last five years at NSA, according to earlier testimony by government witnesses, Pelton was involved in the development of Project A.

Today he said he told FBI agents that the only "precise information" about the project that he had related to its "recording system." Pelton said it was his job "to make sure the recording system was compatible with the signals for which my office had responsibility."

Pelton, who worked for NSA for 14 years, said that he was not familiar with the Soviet communications intercepted by Project A, but rather that he worked on technical problems with the equipment.

In testimony about his interview with FBI agents, Pelton said he pointed out the location of Project A on a map, which has been introduced as evidence under a court seal.

An NSA official testified Friday that the location Pelton circled for the agents -- in response to their request to point out the location he had disclosed to the Soviets -- was several hundred miles off the mark.

In fact, the location Pelton marked on the map for the agents was about 1,000 miles off, according to one informed source.

Nevertheless, other knowledgeable sources have said Pelton's information led the Soviets to discover the interception operation and to seize equipment developed by NSA for the project.

The government's chief witness on the potential harm caused by Pelton's alleged espionage, William P. Crowell Jr., chief of NSA's signals intelligence operations directed at the Soviet Union, gave jurors no specific information on direct damage in the Pelton case.

But Crowell said the kind of information Pelton allegedly disclosed was extremely harmful to national security and allowed the Soviets to capitalize on NSA weaknesses and to understand U.S. intelligence-gathering priorities.

Pelton, 44, was pale and his shoulders were slightly stooped as he took the witness stand this morning to defend himself for the first time against charges that he sold U.S. intelligence secrets to the Soviets in return for $35,000. However, as he began to answer questions he appeared composed and in command of his testimony, which focused on the events surrounding his interview by FBI agents at the Annapolis Hilton. For much of the day he was questioned by Bennett, who sought to show that Pelton, led on by FBI agents, believed that he was being recruited for counterintelligence work.

Judge Herbert F. Murray ruled in a pretrial hearing that Pelton's confession was voluntary and could be admitted at the trial. Bennett is arguing the issue again before the jury, which has been sequestered and does not know of Murray's earlier ruling. Bennett also appears to be preparing for a possible appeal, arguing today that Pelton's testimony in this trial should not be admissible as evidence in any future proceeding.

Bennett scored a minor victory today when Murray acquitted Pelton on one of the six counts in the indictment. Pelton was charged with delivering national security information during his first alleged visit to the Soviet Embassy in Washington in 1980. Murray ruled that the prosecutors had failed to show that the alleged crime was initiated in Maryland and that the U.S. District Court in Baltimore had jurisdiction.

Pelton, who until 1979 was a middle-management NSA analyst with broad access to U.S. intelligence on Soviet communications signals, wrote what the government has termed "an encyclopedia" of Soviet signals while at NSA. The FBI's assertions that he admitted disclosing information in that document, the Signal Parameters File, are inaccurate, Pelton testified today.

When asked by FBI agents which of the signals contained in the file the Soviets were most interested in, Pelton testified, he "declined to discuss it whatsoever. I replied that it would be obvious that the Soviets would be interested in everything in that document."

Project B, which government witnesses have testified is an equipment upgrading program to speed the relaying and analysis of intercepted communications, was hardly worth mentioning to the Soviets, Pelton said. "Why would the Soviets be interested in that ?," Pelton testified that he had asked the FBI agents. He said the project was "nothing more" than the replacement of old NSA radio signal receivers and "demodulators" and an upgrading of the "data link" that would bring those signals back for analysis.

FBI agent David Faulkner, who had interrogated Pelton, testified last week that Pelton described Project B during questioning as an important guide to the Soviets in understanding NSA's operations and long-term capabilities for rapid processing of a large volume of intercepted signals.

Projects C and D were described in earlier testimony by NSA officials as involving secret locations where NSA intercepts Soviet communications.

Pelton testified today that he had, in fact, told FBI agents that he knew these secret locations. However, he testified, during his lengthy debriefing sessions at the Soviet Embassy compound in Vienna, Austria, the KGB officer in charge never questioned him about those projects.

Pelton also has been accused of telling the Soviets about Project E, which has been described in testimony by an NSA official as involving a Soviet signal that carried "command and control" information from the highest level in the Soviet Union. Pelton said that he told FBI agents that the Soviets no doubt would be interested in Project E but that he never told them anything about it and they never asked.

FBI agents, according to Pelton's testimony, pressed him on what information he gave the Soviets on NSA's capability to penetrate Soviet ciphers or codes. "I told them the Soviets I knew nothing about any codes except Morse code," Pelton said, adding with a smile that the Soviets didn't seem to know what Morse code was.

Pelton testified that it was clear that the Soviets put a high priority on learning about U.S. eavesdropping targeted at Soviet embassies and U.S. overhead collection systems, such as spy satellites, but he said that he told them that he could not help them.

"I told them that I had virtually no information involving the first priority and [that] about all I knew about the overhead program was the fact that it existed," Pelton testified.

During his testimony, Pelton denied making a potentially damaging statement that has been attributed to him by FBI agents in affidavits supporting the indictment in the case. According to the FBI version, Pelton said at the end of his interrogation that the Soviets "got more out of me than I wanted to give up."

Today, Pelton asserted that he had never made such a statement but that he had told the FBI agents shortly before they put him under arrest, "You've done a pretty good job because you've gotten me to say more than I should have."

Under cross-examination that got under way late today, Assistant U.S. Attorney John G. Douglass challenged Pelton's assertion that FBI agents in effect tricked him into a confession. Douglass pointed out that Pelton had used terms such as "bargaining chip," "bluff" and "probe" to describe how he tried to negotiate a deal with FBI agents to avoid prosecution.

Douglass pointed out that Pelton made some damaging admissions after he had read and signed a waiver-of-rights form.