Republican congressional leaders told President Reagan yesterday that he may have to make concessions on defense spending to win congressional passage of his latest cuts in non-defense federal programs.

House Minority Leader Robert H. Michel (R-Ill.) said, "I had to tell the president quite frankly that in order to make those significant second-round cuts to the extent that he wanted there might very well be some adjustment in the defense area."

Michel said he is under pressure from House members "of a more liberal persuasion" to increase Reagan's proposed $2 billion 1982 defense budget cut. He said such further cuts would run counter to his personal preference as "the handmaiden of the president."

"I have to be very practical about what is achievable and what isn't," Michel said.

Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) said he told Reagan to expect an effort to cut an additional $1 billion from 1982 defense spending. "I don't think he liked it," Baker said when asked how the president had reacted.

Baker added that the president showed no sign of wanting to back down from his position that defense spending should not be reduced further.

Michel said he warned the president that the first appropriations bill due on the floor since Reagan announced his intention to reduce appropriations by 12 percent, except for certain exempt programs, would be on Labor-Health and Human Services and is between $2 billion and $3 billion above Reagan's new budget target.

"We're going to have to take a run at that in the House tomorrow," Michel said.

Reagan has said he would veto any "budget-busting" appropriation bills that reach his desk.

He said he thinks it is "bad philosophy" to make trade-offs of defense spending for spending on welfare programs, but said there is considerable pressure in that direction.

Baker said he has asked key committee chairmen, including Sens. Pete V. Domenici (R-N.M.), Jake Garn (R-Utah), Robert J. Dole (R-Kan.) and Mark O. Hatfield (R-Ore.) to make recommendations on procedures to follow in seeking the 12 percent appropriations cuts.

Baker said he will have reports from them in a few days, and that he expects to consult on legislative strategy with the White House by the end of the week.

Rep. John J. Rhodes (R-Ariz.) emerged from the morning meeting with Reagan with a low-key report on the White House session.

"I think it was a very nice meeting, but it wasn't particularly productive or impressive. We talked about the general welfare of the country, and sometimes that gets a little dull," Rhodes told reporters.