Lyn Nofziger, the former White House political director, was giving a speech on the 1984 presidential campaign to a group of political consultants from both parties in Room 457 of the Russell Senate Office Building yesterday when he was interrupted by a phone that jangled nearby.

He was told that the call was from Air Force One and that the caller was White House chief of staff James A. Baker III, who was traveling with President Reagan in Latin America.

Nofziger took the call and, without comment, returned to his speech. Twenty minutes later, he was interrupted again and told that the call was from Air Force One. This time, it was Ronald Reagan.

The political consultants all thought it was a monumental bit of one-upmanship by Nofziger. What they didn't know is that the calls were no joke and that this was really the first chapter for Reagan in the nascent 1984 presidential campaign.

Nofziger, now a private political consultant, apparently had surprised the White House with a letter inviting 20 key Reagan campaign operatives from 1980 to "begin preparing now" for the president's 1984 reelection campaign, "based on the assumption that Ronald Reagan is going to seek reelection."

Nofziger asked the political operatives, who were regional directors in the 1980 campaign, to meet him for lunch next Monday, even though the president says he has not decided whether to seek another term -- and even though such reelection planning is usually done inside the White House.

The sharp-witted Nofziger, who has advised Reagan since his first campaign and still retains close ties to the White House, was characteristically candid in the invitation, sent Nov. 22.

"Seems to me that we need to begin preparing now for the campaign, based on the assumption that Ronald Reagan is going to seek reelection," Nofziger wrote. "If he does, I think it is important that the next presidential election be a Reagan-Bush campaign, not a Bush-Reagan campaign.

"For that reason, I thought it might be worthwhile for some of us to get together next month and see if we shouldn't begin to go back and identify our people and try to get hold of the campaign organizations," Nofziger said.

"Frankly, while I'm confident that the president is going to run, I'm not confident that the campaign will be run by Reaganites," he added.

"As you know, when you have an incumbent president, the White House always has the final say on how a campaign will be run," Nofziger wrote. "Nevertheless, I think it important that we try and put together some of the Reaganites as a way of making sure that those who want to be involved in 1984 will be involved."

Nofziger, who as White House political director worked for chief of staff Baker, has made no secret of his feeling that Reagan is getting advice from people not in tune with the president's brand of conservatism. Baker, a target of such criticism by some conservatives during Reagan's first two years, was manager of Vice President Bush's ill-fated presidential bid in 1980. But conservatives have noticeably muted their criticism of Baker in recent months.

Last summer, Nofziger rebelled when Reagan supported a $99 billion tax increase. He organized a Capitol Hill meeting of conservatives who had worked for Reagan and vowed to fight the tax bill. In short order, he was called into the Oval Office by Reagan, and then agreed to help the president engineer passage of the tax bill.

Nofziger did not return telephone calls yesterday. Nor did he reveal to the political consultants he was lecturing what the telephone calls from Air Force One were about.

When the second call came, Joe Cerrell, vice president of the American Association of Political Consultants, to whose members Nofziger was speaking, announce hat "it's Air Force One."

Nofziger shrugged off the message, indicating he didn't want to interrupt the speech again. "It's the president this time," Cerrell said, in earshot of the audience.

Nofziger quickly finished his talk and took the call. The audience of about 100 laughed. Many thought it was a very good joke staged by Nofziger for his peers.

But Nofziger was overheard telling the president, "I'm in a public meeting. Perhaps we could meet privately." It was learned from another source that Reagan had been trying to reach Nofziger yesterday at about the time Air Force One was on a four-hour, 45-minute flight from Brasilia, Brazil, to Bogota, Colombia.

Reagan's pollster, Richard Wirthlin, told reporters at a breakfast meeting yesterday that he was going to the meeting Monday and said he believed the president had no objections to the meeting.

Questioned as to whether the session should be read as an indication that Reagan plans to run in 1984, Wirthlin said it is "a signal, but I don't think it's a definite signal."

An administration source who has a copy of the Nofziger letter said yesterday that it originally appeared to be just a social invitation but, on second look, was obviously more than that.

"I thought it was just a get-together," he said, adding that even as a political strategy session, the meeting "can only go so far" without White House approval.

Among those expected to attend the Monday meeting are Edward Rollins, White House political director, and Lee Atwater, his deputy. Also expected is Frank Fahrenkopf, the current Nevada state GOP chairman and a Reagan loyalist who is slated to become the next chairman of the Republican National Committee. Sen. Paul Laxalt (R-Nev.), who will be "general chairman" of the national committee, was also invited but an aide said he won't be able to attend.