The big diplomatic news of the week was made by three men - Anwar Sadat of Egypt, Menahem Begin of Israel of a fellow from New York known as "Walter" to Sadat and "Mr. Cronkite" to Begin.

Cronkite, a television newscaster, became the medium for the first nearly direct message between an Egyptian leader and an Israeli counterpart in many years - "a real happening", in the words of Marshall McLuhan, the guru of medium and message, who teaches at the University of Toronto.

"I guess Cronkite has assumed a new role - as a diplomat," McLuhan said in a telephone interview.

Cronkite himself demurred. Yes, he agreed, it was an unprecedented event in his career, because no earlier interview or combination of interviews "had the prospect of immediate impact like this." (He referred to the prospect that Sadat will soon visit Israel and address its parliament - the big news of the week.)

But, he added insistently, "I don't consider if a notable scoop . . .It's a technological thing" - a well-timed sequence of interviews.

As far as Cronkite was concerned, principal credit should go to Joel Bernstein. CBS New's bureau manager in Tel Aviv. In less than six hours, Cronkite said, Bernstein set up a live interview with Begin to be relayed by satellite to New York.

It all began at about 9 o'clock Monday morning. New York time, Cronkite said. That was when he conducted a previously arranged interview with Sadat, also via satellite hookup. During the interview, Sadat said he was willing to go to Israel and address the Knesset (Parliament) without preconditions, and as soon as next week.

That was news, Cronkite said yesterday, and worth pursuing vigorously. So the call went out to Bernstein in Israel to try to arrange an interview with Begin. At 3:30 p.m. the Israel prime minister had his chat with Cronkite, during which he promised to send Sadat a formal invitation - through the American embassy - and proposed postpoing a trip to Britain next week so he could receive Sadat.

"We had no lines laid to Begin at all." Cronkite said i the jargon of electronic jounalism. "We had to really scramble."

But wasn't there more to it than that - some symbol in this event of the role of television in our time, or the role of Walter Cronkite as father figure to America, and now the world? Cronkite wouldn't agree with those propositions. He laughed a little when the questions were posed. "I don't know. I think it's immodest personally or for the whole industry to suggest that we have become a force of that nature."

But he would admit that "this is another example of the power of television that people refer to."

Cronkite neted that print journalists have always bounced quotes back and forth between disputing parties - be they statesmen or members of a local school board - in hopes to producing a story. "All that is happening" on television, he said, "is that you're seeing it before your eyes."

Fred W. Friendly, a former president of CBS News and now a journalism professor at Columbia University, agreed.

"It's the best platform around." Friendly said, referring to television in general and the Cronkite evening news show in particular. "I think they (Begin and Sadat) both see themselves as coming across well on the tube. They like to maket their points in their own voices."

Friendly said he wondered whether the exchange had been rearranged. "My own guess is that this scenario was invented somewhere," he said. Cronkite, however, said it all came as a surprise to him.

Over at ABC, the new director of news, Roone Arledge, let it be known that ABC had the story first. Hours before Cronkite interviewed Sadat, Arledge contended, the Egyptian leader made the same remarks to ABC's Peter Jennings in Cairo. And Begin offered to send Sadat an invitation in an interview with Bill Siemens, ABC's man in Israel, before he made the offer in talking to Cronkite. But ABC didn't have it on camera.

Barbara Walters, ABC's star interviewer, said in an interview that world leaders were coming to realize that "television gets it quicker."

Cuban President Fidel Castro recently foretold his decision to release some American prisoners in an interview with her, Walters recalled.

Cronkite agreed that prominent figures now know how to use television. Interviewing is really nine-tenths a question of timing," he added. "You don't get anything out of world leaders that they don't want to give you."

So that's the way it was.