Sen. Harrison A. Williams (D-N.J.) denied to FBI agents the night the Abscam investigation ended last year that he had any interest in a titanium mining venture or ever had been asked to use his influence to get government contracts for the mine, according to testimony at his bribery trial today.

Earlier taped evidence at the trial showed Williams did accept stock in the mining venture and told an FBI agent posing as an Arab sheik that there would be no problem getting government contracts for titanium.

Williams and codefendant Alexander Feinberg are charged with agreeing to trade that senator's influence in getting government contracts for hiden mining company shares they though would be worth $12.6 million.

Government witnesses have testified that the alleged conspirators were seeking contracts to sell titanium, which is a strategic metal in the manufacture of submarines and aircraft.

FBI Agent Joseph W. Vidovich testified that when he and another agent interviewed Williams at his Georgetown home on Feb. 2, 1980, the senator said he was not aware of any other companies involved in the venture except U.S. Titanium Corp., which owned the dormant mine near Lynchburg, Va. "He further told us that if any companies had been formed he didn't have an interest in any such company." Vidovich said. On an Aug. 5, 1979, audio tape introduced by the government last week Williams is heard accepting shares of stock in new companies formed to operate the mine.

Vidovich said that when Williams was asked whether anyone had solicited his support or influence to get government contracts for titanium, "he said 'no.' He said, 'How could there be any government contract if the mine wasn't operational?'"

After Vidovich's testimony, prosecutor Thomas Puccio rested the government's case.

Williams' attorney, George J. Koelzer, began the defense by offering testimony that government agents induced the senator to make statements. He called government attorneys and investigators to describe the conduct of Melvin Weinberg, a convicted con man who is a key undercover operative for the FBI.

Robert A. Weir Jr. and Edward J. Plaza, both assistant U.S. attorneys from New Jersey, said that when Weinberg was warned against putting words in the senator's mouth just before a key June 28, 1979, meeting with the "sheik," he replied: "If we don't do that we won't have no cases."

Weir testified that Plaza had lectured Weinberg "that it was improper to tell someone what to say and then have them go on video tape and say it."

Though he has never used the word "entrapment" in the courtroom, Koelzer appears to be developing his defense along those lines. His efforts are complicated, however, because the government can counter an entrapment argument by showing that the defendent had engaged in similar acts before and was thus predispoed to commit the crime. The government has already entered such evidence about Williams. Koelzer said in his opening statement that the senator was fooled by Weinberg and the other government agents.

After the jury left for the day, Koelzer and his associates argued that the key bribery counts should be stricken from the indictment because the evidence showed the stock the senator received was worthless. Bribery law reqires that an official receive "something of value" in return for using influence.

Puccio countered that the jury could conclude that the stock was very valuable to the defendants because of the undercover agents' promise of the $100 million loan.

U.S. District Court Judge George C. Pratt said he would consider the motions overnight and rule before the trial resumes Friday.