Ronald Reagan, entering the third year of his presidency, is resisting pressure from longtime conservative supporters to send a message that he will seek a second term.

Presidential intimate Sen. Paul Laxalt (R-Nev.), handpicked by Reagan to become general chairman of the Republican Party, said last week that Reagan should not be "stampeded" into announcing his intentions for 1984 before he is ready, despite conservatives' insistence that he give an early signal.

Administration officials said this view apparently reflects the opinion of the president, who has no plans now to make any announcement.

"I don't feel any imminent need of [Reagan] sending a signal," said Laxalt, who also reaffirmed his belief that the president will seek a second term.

Others said Reagan has not decided and probably will not until this summer. Two advisers said they expect reelection to be a prime topic at a meeting of strategists, advisers and friends that probably will be held in California in August. Reagan presumbably then would give a firm signal of his intentions by Labor Day.

Conservatives have been urging Reagan publicly and privately to let his supporters know his intentions so they can begin mobilizing. Supporters of Republicans who are prospective candidates if Reagan does not run also would like an early warning.

Yesterday, Senate Majority Leader Howard H. Baker Jr. (R-Tenn.), who has said he will not seek a fourth term and may seek the presidency if Reagan does not run, said he hopes the president will announce his intentions early because it "helps the political atmosphere and even the situation in Congress to know what the president is going to do."

"The president should give a good strong signal," said former political adviser Lyn Nofziger. "He will be more effective with the Congress, particularly the Republicans, if they think they're not dealing with a lame duck.

"Secondly, there's a lot of restlessness out there with his troops. And in fairness to the others who would want to run if he didn't, they ought to be told. The election is nearly two years away, but the campaign will be on top of us before we know it."

White House aides, most of whom publicly predict that Reagan will decide to run, say privately that it would be a mistake for the president to give a signal now because it would look "too political."

They note that Reagan is entering a phase of his presidency in which he is trying to win bipartisan cooperation from the Democratic congressional leadership for important elements of his budget rather than relying on the conservative coalition that carried him through the first two years.

And there are some, although not in a majority, who think the president is not sending a signal because he is thinking about stepping down after a single term.

One longtime Reagan adviser said recently that "for the first time, I have doubts whether he will run." He said the doubts are based on a feeling that Reagan will have "had enough of being president," particularly if the economy improves and he can retire on a positive note.

Most aides and advisers agreed that Reagan is more likely to run under adverse circumstances, if his presidency is widely perceived as a failure, than if economic conditions improve to the point that he can make a credible argument that his policies are working.

Because of Reagan's well-known optimism, one adviser observed, the president will "be able to make a positive case" for situations that others might find negative.

The top aide considered closest to the president, deputy chief of staff Michael K. Deaver, has predicted flatly that Reagan will run again. White House counselor Edwin Meese III and chief of staff James A. Baker III have said they expect him to seek reelection even though he has not made up his mind.

National security adviser William P. Clark, who has worked for Reagan since his first campaign in 1966, is known to have said recently that "the president isn't a quitter--he's not going to walk away and leave work unfinished."

While most of the discussion and speculation inside and outside the White House centers on the condition of the economy, some close to Reagan say the state of U.S.-Soviet relations also will be important in his decision.

According to one source, Reagan would be especially inclined to run again if an arms-control agreement was in the works but not completed or ratified, or if he thought his successor likely to abandon his defense policies.

The view of those who want and expect Reagan to run was expressed by Nofziger:

"There's no reason for Ronald Reagan not to run again. He's not going to get everything done he wants to in his first term . . . . He doesn't show his age. People say that Nancy doesn't want him to run again. But if he wants to, she will support him as she always has.

"As Sen. Bob Dole R-Kan.) used to say about the vice presidency, the hours are good, and there's no heavy lifting. There's no place to go after the presidency but home."

Baker said last week that Reagan "really enjoys" the presidency, adding that "he obviously enjoyed it more when everything was going swimmingly, but he still enjoys it."

Meese said Reagan has aged less in the job than other presidents because "he keeps himself healthy and has a personality that doesn't lend itself to constant emotional drain."

But those in the entourage who wonder if the president will seek another term often mention his age.

Reagan will be 72 on Feb. 6. If he won reelection, he would be nearly 78 at the end of a second term.