President Reagan, bidding farewell to his chief arms negotiator yesterday morning, compared the strategic arms reduction talks (START) that begin Tuesday in Geneva to his tough bargaining sessions with the "tycoons of the movie business" as head of the Screen Actors Guild in the 1940s and 1950s.

"Somebody once said about our labor negotiations, 'We're asking for the moon, they offer green cheese and we settle somewhere in between,' " Reagan told reporters allowed briefly into the Oval Office as photos were made of his meeting with Ambassador Edward L. Rowny, head of the U.S. arms reduction negotiating team.

Reagan said he is "cautiously optimistic" about the outcome of the Geneva talks with the Soviet Union but said later in a formal statement that he does not "underestimate the formidable nature of this task."

But, he told reporters, "No agreement is better than a bad one."

Reagan seemed to want to prepare Americans for negotiations that would be neither easy nor quick and apparently wanted to indicate that patience is a necessity if the United States is to be an artful strategist.

He observed pointedly that the slow and cerebral game of chess is popular in the Soviet Union while the rapid-fire video game "Pac-Man" is the rage in this country.

Rowny, in several press briefings, has also stressed the belief that the talks will be slow and tedious.

Yesterday, in a rare move, White House reporters declined an opportunity for another briefing on the arms talks because the White House declined to permit journalists to identify the briefing official by name, saying he could be described only as "a senior administration official."

"We want on-the-record," several reporters said emphatically.

Deputy White House press secretary Larry Speakes responded firmly, "You ain't going to get it."