Rep. John W. Jenrette (D-S.C.), under pressure from federal prosecutors to explain why he continued to talk to an FBI undercover agent after the man offered him a $50,000 bribe, gave a wide array of reasons yesterday.

He was drunk, he testified, and convinced he was dealing with mobsters. He was trying to help an old friend and save 500 jobs, and scared he would be found floating in the Potomac. And finally, he said, he was stalling for time to lay his own trap for the FBI agent.

Jenrette, 44, on trial in U.S. District Court for conspiracy to accept bribes from the representatives on a phony Arab sheik, told the jury that he thought if he stalled long enough he would eventually catch the undercover agent, Anthony Amoroso. Amoroso was posing as Tony DeVito, a man who Jenrette thought was a mobster.

During lengthy cross-examination yesterday by government prosecutor John Kotelly, Jenrette testified that he wanted to "find some way to set DeVito up and find out who he was." Eventually, Jenrette testified, "I was going to . . . turn him in."

Jenrette testified that he made statements about laundered money and a CIA friend in Libya -- all captured on secret FBI tapes -- because he thought it was the kind of talk that mobsters like to hear.

The congressman's statements were the first testimony in his trial, now five weeks old, that Jenrette may have been pursuing his own investigation into the payoffs offered by the agents for the fictitious Arabs.

Jenrette and a codefendant are on trial for conspiracy to accept payoffs in exchange for Jenrette's promise to introduce private immigration legislation for fictitious Arab sheiks. The prosecution is one in a series stemming from the FBI's undercover "sting" operation called Abscam, for Arab scam.

Yesterday, prosecutor Kotelly confronted Jenrette with portions of tape recordings in which the congressman discussed a $100,000 payoff with Amoroso, suggested he might have his law partner pick up the cash and later told Amoroso that he was "ready to go forward" with introduction of a private immigration bill.

But, Jenrette testified in response, he was "shocked" when Amoroso brought up the money, although he acknowledged to Kotelly that he did not seem to be shocked on secret FBI videotapes of the conversation. Jenrette testified that he couldn't recall making other statements, although there was no disputing they were on the tapes, that he might have been intoxicated and that he was conjuring up excuses in the taped conversations because he was frightened.

"Mr. Kotelly, I was drunk, I was afraid, I was scared, I would have told him [Amoroso] anything to get out of there," Jenrette said in reference to a meeting last December where the payoff was discussed.

Jenrette denied that he and his codefendant, former Richmond businessman John R. Stowe, discussed the payoff deal at a lunch at the Monocle Restaurant on Dec. 4 before they went to the meeting on W St. N.W.

Under questioning from Kotelly. Jenrette told the jury that as far as he was concerned he was going to the W Street house to meet with people that Stowe knew were interested in investing in a failing munitions plant in Jenrette's home district. According to evidence in the case, Stowe hoped to obtain loans from the Arabs to buy the plant. This, Jenrette said, would have saved 500 jobs.

Jenrette said he had no idea that he would be offered money at that Dec. 4 meeting and that he was only trying to help Stowe in attendingg FBI videotapes showed Stowe at the house two days later where he picked up $50,000 in cash from undercover agent Amoroso. Stowe said on the tape that he was on his way to Jenrette's Capitol Hill office.

Jenrette's defense lawyers have tried throughout the trial to focus the burden of the conspiracy and bribery case on Stowe.

Jenrette's defense lawyers contend that Stowe used the congressman to try to secure loans from the Arabs to shore up the South Carolina munitions plant. They argue that Jenrette, who is troubled by alcoholism and debts, was an easy victim for the FBI undercover operation.

Yesterday, Stowe's lawyers tried unsuccessfully to convince Judge John Garrett Penn to give their client a separate trial. Stowe's lawyer, Murray Janus, told Penn that Stowe's is being forced to defend himself against Jenrette as well as the government.

Janus told Penn that he will try to show that Stowe was a victim of FBI "entrapment" because he was induced by FBI undercover agents to join in a scheme when he had no predisposition to commit a crime.