President Reagan yesterday said he will announce soon whether he will run for reelection, and told a gathering of eastern Republican Party leaders who are preparing for the 1984 election that they need not fear criticism that the administration is unfair to the poor.

At the conclusion of a closed-circuit television conference from the White House with the party officials, who included state chairmen and fund-raisers, the president was told by Republican National Chairman Frank J. Fahrenkopf that the group wants "four more in '84."

Reagan laughed and said: "You understand why I don't respond to that right now, but we'll be talking about that before too long."

The president gave the party officials, who were at the Mayflower Hotel, a spirited defense of his administration--particularly on the fairness issue--only four days after a speech in South Carolina in which he attacked the Carter administration for leaving the nation's house "on fire" and denounced "liberals" and "misery merchants" for not recognizing his administration's successes.

"I asked two questions during the last campaign and you'll probably be hearing them thrown back at you in the months ahead," the president said. "Are you better off than you were before? Do you feel America is more secure than it was?

"Well," he continued in a stern voice, "I welcome those questions, and I hope you do too, because as I said this week in South Carolina I think it's time we held our heads high and made our case to the people. Yes, we are better off than before and, yes, America is more secure today than in 1980."

After saying that his critics should stop their "whining and complaining," Reagan told the party leaders the proof of his success was in lowering the inflation rate from 12.4 to 2.6 percent, lowering the prime interest rate from about 21 to 11 percent and enacting tax cuts "because permitting the middle-income family to keep $700 more of the money it earns is better than the big built-in tax increases condoned by the last administration."

The president then attacked Democrats for seeking to take advantage of the record $200 billion federal deficits built up under his administration.

"Let's tell the truth about our critics," he urged. "They sob enough about deficits to fill an ocean. But it is an ocean of crocodile tears. What they are after is a blank check for higher taxes, more spending and greater control over the people's lives.

"They say they plan to talk about fairness," he added. "Well, fine, let them."

In response to a question about charges that the administration has been unfair to the poor, Reagan said that talk about the lack of fairness in the administration was based on "political demagoguery."

He said administration critics cannot substantiate claims that his tax policies have favored the rich.

"It was across the board," he said. "The same percentage cut . . . ."

Reagan added that his budget cuts were necessary to reduce deficits.

"We have never gotten all that we asked for in that regard and we are still going to try for more," he said. "So they don't have a leg to stand on on any charge of fairness. What they should be defending is how could they call it fair to have gone along with their deliberate planned inflation and their deficit spending?

"You know, with their sobbing about the prospective deficit now, are we to forget how they used to tell us that the national debt didn't matter because we owed it to ourselves and that deficit spending was necessary to maintain prosperity?"