Confronted by the FBI, accused Chinese spy Larry Wu-Tai Chin offered to work as a double agent for the United States and provided details of his alleged espionage when FBI agents told Chin he would "have to disclose everything that had occurred" before authorities could decide whether to use him as a double agent, prosecutors said in papers filed yesterday.

The document, which offered the first account of how agents allegedly persuaded Chin to admit spying for the Chinese, was filed in Alexandria federal court in response to defense lawyers' bid to block prosecutors from using the statements at Chin's trial.

A retired analyst for the CIA, Chin made the statements Nov. 22 in a six-hour interview with FBI agents in his Alexandria office that ended with his arrest. He is charged with spying for the Chinese from 1952 until he was taken into custody.

The government's response to the motion to suppress Chin's statements also contained the first hint of how the government's case against Chin might have developed.

At one point during the evening, according to the document, Chin asked agents, "How do I know you're not bluffing?" In response, one of the agents, Mark R. Johnson, described a meeting in Hong Kong in September 1983 in which Chin allegedly gave Chinese intelligence agent Ou Qiming the name of a fellow CIA employe who he thought might be recruited as a spy.

"After hearing the details of the trip, including a discussion that he had with Ou about Chin's marital difficulties, Chin said the details about his wife were known only by Ou . . . and speculated that Ou had defected," prosecutors said.

The government has not disclosed how the investigation of Chin started, although sources have said it involved a CIA counterintelligence program.

The document filed yesterday provided this account of the evening:

Three FBI agents arrived at Chin's Alexandria office about 4:25 p.m. and said they wanted to talk to him about an investigation into "the passage of classified information." Chin responded, "Why sure, come on in."

Chin at first "denied any contact" with Chinese intelligence agents. The agents related details of Chin's alleged meetings with officials of the Chinese intelligence service.

They told him "they had been investigating this for a long time and that they had come to him to offer him a chance to explain what had happened" and describe any possible "extenuating circumstances," prosecutors Joseph J. Aronica and Kent S. Robinson said in their response.

The agents told Chin he was free to call a lawyer, that he was not under arrest, and that they would leave if he liked. However, they said, if he did not want to talk, they would continue the investigation.

When Chin inquired why he should cooperate, the agents told him the story of two individuals, one who had cooperated and one who had not. "They then asked Chin, 'Now if you were the Department of Justice, which one would you have more sympathy for, the individual who slammed the door in the agent's face or the one who said what had happened and said he was sorry?' " according to the document.

Chin asked for time to think the matter over, and the agents told him "this was his only chance to cooperate." He then offered to work as a double agent, and began outlining his political activities starting in 1943.

Chin was "exceptionally calm and cool about how he had done everything," the prosecutors said, "and stated that if he had to go to jail it would be good because he could catch up on his reading and write his memoirs."