The FBI agents working on a planned sting against then-D.C. Mayor Marion Barry said their supervisors were pressuring them to move along the investigation and wanted "more concrete information on Barry to nail him," according to a journal kept by a government witness aiding in the probe.

The journal, maintained last year by then-D.C. police Lt. Yong H. Ahn, provides his day-to-day account of the FBI's plans to catch Barry in the act of accepting money in return for a D.C. government job. The sting was never carried out, and Barry was never charged with any wrongdoing. Barry yesterday formally demanded an explanation from the Justice Department.

In one passage, Ahn quotes the FBI agents as telling him "their boss want this investigation to move forward" by having Ahn's wife, Azita, approach Barry for a job "and pay him off. . . . They (FBI) will pay for the bribe money and me and my wife have to be wired. Their boss want them to move on with this investigation and they are under lot of pressure."

Yong Ahn, a former D.C. police officer of the year and once the highest-ranking Korean American on the force, turned government witness after the FBI arrested him in February 1998 on charges that he took $8,000 in bribes from the operators of illegal massage parlors. Details about the sting plans had long been kept secret but emerged within the last two weeks, after a federal judge unsealed records in Ahn's criminal case. Ahn was given a four-month sentence last month, having received credit for his assistance to investigators.

The journal, obtained by The Washington Post yesterday, covers key events from March 25, 1998, through April 23, 1998, when the sting plans were abandoned. That day, two television stations disclosed that Ahn had been arrested. Despite Ahn's contention that the sting against Barry was imminent, federal prosecutors have said they never signed off on the operation.

Ahn kept records at his attorney's request to document his assistance in the probe. According to Ahn's notes, he met three times with businessman Ho Kang, a Barry supporter, and won Kang's agreement to act as the middleman in the job-for-cash plan. During two of the meetings, Ahn wore a recording device, the journal stated. Ahn wrote that Kang agreed to invite Barry to his house in Burke, where the meeting with Barry supposedly would take place. The plan called for Azita Ahn to pay $5,000 in return for a D.C. job, he wrote.

Kang did not return two telephone calls to his business yesterday.

According to a court transcript unsealed earlier in Ahn's case, Ahn had testified at a hearing that FBI agents initially had asked him about another D.C. businessman and Barry ally, Tony Cheng. In later passages, the transcript quotes Ahn as saying that "Cheng" was to be the middleman in the sting. Azita Ahn said yesterday that the references to Cheng were a court reporter's error and that the transcript confused Cheng with Ho Kang. She said, "Tony Cheng had nothing to do with this sting whatsoever."

In his journal, Ahn wrote that FBI agents William H. Spivey Jr. and Daniel J. Foore had him contact Kang repeatedly because the agents' supervisor and D.C. police "want more concrete information on Barry to nail him before FBI can come up with $5,000." He said the agents ultimately were pleased with the results of his work and "said now we have great evidence and their boss will be very happy." The journal does not identify the "boss" or supervisors.

FBI officials have declined to comment on the investigation. Foore works in the Washington field office's public integrity section. Spivey has been on administrative leave for more than a year because of allegations stemming from another police corruption investigation.

The journal includes Ahn's account of a pivotal meeting with the FBI agents and Robert R. Chapman, a federal prosecutor in the District who was overseeing Ahn's case. Ahn said that during the meeting, Spivey showed Chapman a copy of a phony resume prepared for Azita Ahn. But the journal mentions nothing about Chapman's reaction and has Chapman focused on questions about other potential targets. Other law enforcement sources have said federal prosecutors believed the FBI didn't have a foundation to pursue a Barry sting.

Ahn quotes Spivey and Foore as saying Chapman was scared of the case because it was "too much work and too political." According to Ahn, the FBI agents said the federal prosecutor's office in Northern Virginia was "very eager to prosecute the mayor" and Barry would "not get off easy" there.

Barry, who did not run for reelection last year, was the focus of numerous FBI investigations during his four terms as mayor. He was convicted only once, of a misdemeanor drug charge in the case that followed his arrest in a sting operation at the Vista Hotel in January 1990.

Helen F. Fahey, the U.S. attorney for the Eastern District of Virginia, expressed surprise at the journal's entries yesterday and said her office had no role in the Ahn case. "No one ever came here from the FBI and asked us to authorize an investigation or any kind of sting operation," she said.

Barry, who has expressed outrage at the FBI's tactics, yesterday formally asked Attorney General Janet Reno to investigate the matter. In a letter to Reno, Barry attorney Frederick D. Cooke Jr. complained that FBI agents engaged in "conduct which clearly constitutes entrapment" and said it was part of a long-running and ill-founded effort "to get Marion Barry."

"The efforts of some in [the Justice Department] have gone far beyond fair or rational scrutiny," wrote Cooke, a former D.C. corporation counsel and longtime Barry adviser. "The use of significant DOJ resources to investigate rumor or innuendo regarding Mr. Barry has certainly proven to be fruitless and would seem to be driven by something other than rational thought."

John Russell, a Justice Department spokesman, said officials will review Cooke's letter and respond. He declined to comment further.

CAPTION: Marion Barry's attorney has written a letter demanding an explanation.