Commissioner Pete Rozelle of the National Football League spent nearly five hours on the witness stand in federal court today and -- despite prodding by the lead attorney for the U.S. Football League -- denied any implication that the NFL illegally "tied up" all three major television networks.

USFL attorney Harvey Myerson called Rozelle as his first witness and spent the entire session trying to discredit Rozelle and to establish conspiratorial behavior by the NFL against the USFL. Later, Myerson said he expected Rozelle to be on the stand through Friday.

On this second day of trial of the USFL's $1.32 billion antitrust suit, Myerson went back and forth on a variety of points raised in his opening statement Wednesday. He pressed the USFL contention that the NFL had an anticompetitive intent in several interoffice memos, in negotiations with television networks and in a Harvard Business School seminar attended by 65 NFL officials in 1984.

Since moving from a spring schedule to the fall of 1986, the USFL has been unable to secure a network contract.

Besides damages, the USFL is seeking injunctive relief to force the NFL off at least one network so that the USFL might negotiate a deal of its own with that outlet. Judge Peter K. Leisure presides over the trial, which is expected to last until mid-July.

Rozelle denied that he negotiatied the NFL's current $2.1 billion, five-year contract with the three networks in 1982 with the intent to cut off the financial lifeline to the USFL, just as that league was preparing to announce its creation.

Myerson asked if it wasn't true that both the length of the NFL's five-year package (one year longer than any previous NFL deal with the networks) and its inclusion of a third network, ABC, in the annual Super Bowl rotation were done specifically to stymie the USFL.

Rozelle responded that he wanted to negotiate a lengthy network deal in 1982 because the NFL had enjoyed record television ratings and attendance the previous season, so "I felt it was to our advantage to reach out for a longer period."

By adding ABC to the Super Bowl rotation, Rozelle testified, his league was able to secure more money from ABC for the network's regular season package and the NFL then could use the figures from the ABC total package as leverage in negotiations with NBC and CBS.

As Myerson questioned the clarity of Rozelle's memory, the commissioner said, "You don't forget things that add up to $2 billion."

Myerson introduced as evidence a Feb. 9, 1982, memo sent to Rozelle from Don Weiss, NFL executive director, that indicated the USFL was about to announce its formation. However, Rozelle said the memo had no bearing on his negotiations with the networks, which concluded one month later.

"It didn't even cross my mind," Rozelle said of the USFL. "What was being proposed by the USFL was a spring league and the contracts with the network were not exclusive."

At one point, Myerson asked Rozelle if he received "a very substantial tax-free bonus" from NFL owners, after negotiating the network contract in 1982. Rozelle said he received a "bonus payment" but it was not tax-free, at which point Judge Leisure sustained the objection of NFL attorneys. (On Wednesday, NFL attorney Frank Rothman had stated that USFL Commissioner Harry Usher earns a $300,000 annual salary and could receive as much as $3.2 million if a merger between leagues took place. Usher admitted such a merger clause existed in his contract, but termed the $3.2 million figure "inaccurate.")

Myerson introduced a 1984 letter sent to a Harvard Business School professor by Sargent Karch, counsel to the NFL Management Council, recommending that the seminar presentation on "how to destroy the USFL" -- as Myerson put it -- be extended from "one hour to 2 1/2 hours."

Rozelle said he did not know that the USFL was going to be discussed during the seminar.

One of the six jurors, a male post office distribution clerk, was excused today for personal reasons. He was replaced by a retired Westchester County woman, so five of the six jurors are women.