Government prosecutors yesterday played a secretly recorded tape of a conversation in which Washington defense lawyer William A. Borders Jr., accused of negotiating a $150,000 bribe for a federal judge, took $25,000 in cash from an FBI undercover agent and then haggled with him about the terms for the rest of the payoff.

The first clues to the defense case also appeared today when Borders' lawyer, John A. Shorter Jr., strongly suggested during questioning that Borders, like the agent, was playing a role in order to get the money that the agent had promised him.

Borders is charged with conspiring with U.S. District Judge Alcee L. Hastings in Miami to take the bribe money from convicted racketeers Frank Romano and his brother Thomas.

In exchange, the government contends, Hastings ordered the return to the Romanos of $845,000 they had forfeited to the court. In addition, prosecutors say, Hastings planned to reduce three-year prison terms he had imposed on both of them after a trial in his court.

"What is it in?" Borders asked undercover agent H. Paul Rico who was posing as Frank Romano when Borders arrived at the Miami airport on Sept. 19, allegedly to pick up the first installment of the bribe.

"Ah, it's . . . it's just in an envelope. I'm gonna put it inside the, the newspaper and . . . ah, give it to you," replied Rico, a short,stocky man with short cropped white hair who was summoned out of retirement for the operation because he resembles the real Frank Romano.

Rico testified yesterday that he put the envelope with the money--in $100 bills--on the arm of a couch at the Miami International Airport, where he had met with Borders.

"Um, oh, there's . . . there's 25, ah right there and that's going to be my understanding that . . . ah everything is fine . . . when the next transaction takes place in 10 days, I'll come up with another 25 and the remaining 100 on the culmination," Rico said on the tape, which was played for the jury here today.

"That's different than what we had said," Borders replied, according to the tape. "What about as soon as the other is done? Get it all up . . . ."

Several times during his questioning of Rico and other witnesses Shorter tried to disassociate Borders from Hastings and raised the suggestion that Borders, rather than conspiring with the judge, was merely trying to con money out of the man he thought was Romano.

"If he Borders was fooling you, he did a pretty good job of it, right?" Shorter asked undercover agent Rico during cross-examination.

"I didn't believe he was playing a role," replied Rico.

Earlier during yesterday's proceeding, the jury heard another tape recording in which a former client of Borders, North Miami antique dealer William C. Dredge, introduced him to "Frank Romano," actually undercover agent Rico. Unkown to Borders, the undercover operation began when Dredge allegedly informed the FBI that Borders had told him Hastings was soliciting bribes from defendants who had appeared before him and that Borders would act as a middleman. After contacting the FBI, Dredge allegedly offered to set up a contact between Borders and Romano.

"How you doing? What's your name again?" Borders asked when he was introduced to Frank Romano, according to the tape. "I understand you had a problem . . . I think we can help you."

"I hope so," the undercover agent replied.

"Ah, you know what the number is, right?" Borders said on the tape. According to Rico's testimony today, Borders then took an envelope from his pocket and wrote "$150,000" on it.

Hastings, according to government testimony, signed the order releasing the Romanos' forfeited funds on Oct. 6. Three days later, Borders went to the Marriott Twin Bridges motel in Arlington to meet Rico (posing as Romano) and allegedly collect the remaining $125,000 of the payoff.

As the jurors listened to the tape they heard Borders rap on the motel door and then say to Rico "You got it with you?" Rico testified that he had the money in a red suit bag in the room which was wired for audio and video. Borders did not step inside.

"Come on. Get it . . . I wanna take a ride," Borders said on the tape.

Inside Borders' car, the two men exchanged small talk about the weather while the car radio and the seat belt signal were heard in the background. Rico testified that the red bag with the $125,000 was on the floor between them.

Within minutes, the tape was full of the sounds of wailing sirens. The FBI, surprised that Borders did not enter the motel room, had decided to arrest him immediately.

"We're busted," Borders said on the tape to Rico as the sirens blared.

"I'm afraid so," Rico replied.

"Okay," Borders said.