An FBI agent who interviewed accused spy Ronald W. Pelton for five hours shortly before his arrest early Monday testified yesterday that Pelton initially denied passing U.S. intelligence secrets to the Soviet Union, but gradually, over the course of discussions, admitted he had sold highly classified information to Soviet agents.

FBI agent David E. Faulkner described his conversations with Pelton during a detention hearing yesterday in U.S. District Court in Baltimore.

Magistrate Daniel E. Klein refused to release Pelton on bond, citing the seriousness of the charges and the risk that Pelton would flee the country if released.

In arguing for his client's release on bond, defense attorney Fred W. Bennett said Pelton's employer at Safford Yacht Sales in Annapolis, Brian MacAnanny, a longtime friend, was willing to post $50,000 bond, and Pelton's parents, a retired couple who live in Michigan but are spending the winter in Arkansas, are willing to put up $5,000 of their limited savings.

In addition, said Bennett, Pelton's wife, Judith, from whom he separated in September, was "ready, willing and able" to have Pelton move into the family home in Gaithersburg. Judith Pelton is employed as a nursing supervisor at the Circle Manor Nursing Home in Kensington, Bennett said.

Agent Faulkner said he and agent Butch Hodgson, unarmed and dressed casually, summoned Pelton on Sunday morning to Room 409 of the Annapolis Hilton, where they talked with him for four hours. They met with Pelton again late that evening for a second interview that lasted more than an hour.

Pelton, 44, a former National Security Agency communications specialist, was arrested shortly after midnight. He had top-secret clearance with the NSA, which is the largest and most secret of U.S. intelligence agencies.

Faulkner said the agents first laid out a narrative for Pelton, describing his alleged espionage activities. At first, said Faulkner, Pelton denied the allegations, and then began to "talk hypothetically" about them, saying they did not apply to him.

About an hour into the interview, said Faulkner, Pelton began admitting he had sold intelligence information to the Soviet KGB, and he made further, more damaging admissions in the second interview that night.

Warren Brown, one of Pelton's court-appointed lawyers, questioned Faulkner about whether he and Hodgson had tried to mislead Pelton by suggesting that they wanted him to become a double agent.

"You asked him if he was willing to do some work against the Soviets, isn't that correct?" asked Brown.

"That's not correct," said Faulkner.

Defense attorneys also suggested that Pelton was intoxicated during the interview Sunday night, but Faulkner said Pelton had "indicated that he had had one or two drinks but that he was fine."

Judith Pelton and the couple's eldest child, 21-year-old Paula White, sat behind the defense table at yesterday's hearing. Both looked tense but showed little emotion.

Bennett said Pelton moved to Maryland in 1965, after being honorably discharged from a four-year tour of duty in the Air Force and working for a year in his native Michigan. He joined the NSA and was sent by the agency to England from 1966 to 1972.

According to friends interviewed yesterday, after he left the NSA in 1979, Pelton started trying to sell a device that he claimed would dramatically cut gas usage when installed on car engines. "He almost begged me to put it on my car to show what it could do," said Quay Williams, who rented a house to Pelton and his family in Bowie about 1980, shortly after Pelton declared bankruptcy.

Pelton then tried selling boats, cars, real estate, computer consulting work, nutritional and fitness counseling and what one friend calls "international money shuffling."

"He had all these different ventures and I was never quite certain about what they were," said Paul Gayet, who rented a house in Silver Spring to the Peltons from about 1980 to 1982 and kept in frequent contact with Pelton afterward.

"He had high hopes of finding some real big deals," Gayet said. "But he was never able to pull it off."