In a move that both White House officials and press historians believe is unprecedented, President Carter yesterday appealed to "American journalists and news organizations to minimize, as severaly as possible, their presence and activities in Iran."

The president's request, announced at his news conference, was intended primarily to increase Iran's sense of isolation and of being cut off from much of the world community, officials said privately.

They said it was meant neither to reflect administration unhappiness with U.S. news reporting nor as a warning to American news organizations to pull their correspondents out because of possible forthcoming U.S. military actions.

George Reedy, Nieman professor of journalism at Marquette University in Milwaukee, said in a telephone interview that he didn't think yesterday's appeal had any precedent, including the voluntary censorship practiced by the press during World War II.

"I don't think this has any precedent because it is not to preserve national security but to further the ends of foreign policy," said Reedy, who once was a press secretary to President Johnson.

William Small, president of NBC News, said in an interview: "Our obligation is to report the news as fully and objectively as possible. That obligation remains."

An ABC official said "the government should not tell us what to do or how to do it, except in times of war or dire national emergency. And the president and very clear that this was neither. We would hope that he would be very clear about letting us exercise our news judgements and not his policy judgments."

An official of CBS News said the Iranians had already cut the network's staff but that CBS "will continue to provide the fullest possible coverage of this story, which is of such major importance to the American people."

Washington Post editors said the paper "will keep its one correspondent in Iran for as long as it can to continue to report from that country."

In making his appeal, the president basically excluded journalists from a ban on new travel to Iran and on financial transfers to Americans there, and put his call to the press on a voluntary basis.

Carter's overall restrictive measures for U.S. citizens in dealing with Iran, officials said, grow out of a sequence of executive orders and Section 211A of Title 22 of the U.S. Code.

A senior government lawyer said that a 1964 Supreme Court case, Zemel vs. rusk, upheld the president's power to impose geographic limitations on citizens movements.

However, White House officials said that the question of whether to include journalists in his action -- in other words to force their return from Iran -- was the last matter settled of those decisions announced yesterday.

They said it was decided to exempt journalists for both policy and practical reasons and because a court challenge over First Amendment rights under the Constitution was viewed as certain.

White House aides said the appeal was also meant to deny the Iranian militants holding the American hostages access to U.S. television. The administration believes that the militants like such coverage and cite as evidence the invitation to U.S. reporters to return to Iran in February after having been expelled in January.

The question of the effect of television on the crisis has frequently been debated. Some journalists believe that the militants depend more on Iranian television than on U.S. television and that a U.S. cutoff would not isolate Tehran because TV crews are there from many other western countries.

In making his appeal to the press yesterday, the president said it was "my responsibility and obligation, given the situation in Iran" to ask for the press cutback. It was also said privately that the sheer presence of the journalists -- viewed as U.S. citizens -- complicated an already complex situation.

The administration's legal explanation yesterday about authority to stop reporters if necessary from going places appears to conflict with a comment Saturday by White House counsel Lloyd Cutler.

In discussing the U.S. boycott of the Moscow Olympics with journalists, Cutler said: "I don't know any way to stop reporters."