President Reagan and Republican congressional leaders pointedly disagreed yesterday on whether the forthcoming budget should include a one-year delay in Social Security cost-of-living increases, but they agreed to offer a 10-percent cut in their own pay as a symbolic gesture toward trimming the federal deficit.

Reagan pledged in his reelection campaign not to tamper with any aspect of Social Security, but his fiscal 1986 budget proposes a one-year delay in all other inflation adjustments, including many programs for the poor. At yesterday's private meeting, the Republicans pressed him, on grounds of evenhandedness, to do the same in the giant Social Security program, officials said.

They also urged the president to slow his defense buildup. Reagan was noncommittal on defense but responded sharply on Social Security by saying that the Republicans "should not fall into the trap of proposing any changes" in the retirement and disability system, according to sources who were present.

Reagan told the GOP leaders that a major lesson of his first term was that Democrats would use the politically volatile Social Security issue against Republicans and that changes in Social Security are "going to have to come from somewhere else," the sources said.

White House spokesman Larry Speakes said later that Reagan "will not propose" any changes in Social Security. Asked if Reagan would veto a bill with a one-year cost-of-living adjustment (COLA) delay, Speakes said the question was "hypothetical" and added:

"There have been expressions but there is certainly no concrete evidence Congress is willing to take that step, or particularly the Democratic Party is willing to take that step, and I'm not going to deal with hypotheticals until I see the Congress stick its neck forward."

"The president has made it emphatic that he will not touch Social Security in any shape or fashion, and if you want to go down that road again you're going down the wrong road. What the Congress is going to do, I have no idea, and they don't either," Speakes said.

Incoming Senate Majority Leader Robert J. Dole (R-Kan.) told reporters after the meeting with Reagan that a one-year delay in the Social Security cost-of-living adjustment would produce $7 billion in deficit savings in fiscal 1986, $10 billion in 1987 and another $10 billion in 1988.

Dole said "that's a rather big item," but he noted that Reagan had balked and "that's sort of where we left it. There is a general feeling that we ought to take a look at that and see if there's any bipartisan support on the Hill, but the president hasn't suggested that at all."

"It has been looked at in Congress before. In fact, there are Democrats and Republicans who suggested it last year," Dole said, referring to the deficit-reduction effort as "sort of an emergency measure."

"My view is that basic benefits are protected," he added in response to a reporter's question about Social Security. "COLAs cost-of-living adjustments are something else, and maybe we ought to take a look at COLAs."

Senate Budget Committee Chairman Pete V. Domenici (R-N.M.) also raised the possibility of a one-year Social Security COLA freeze earlier this week.

The Social Security system is self-contained in that its taxes can be spent only for benefits, and surpluses accumulate. But the taxes count as federal revenues and the benefits count as spending. If spending is lowered through a OLA delay, the deficit's size is reduced.

The idea of a 10 percent pay cut for members of Congress, the president and top political appointees was floated by Dole and House Minority Leader Robert H. Michel (R-Ill.) the day after Reagan told his Cabinet that he will seek a 5 percent cut in federal civilian pay.

Michel said a 10 percent pay cut for top officials would be good "imagery" in light of the broad pay cut. Speakes said later that Reagan "would go along with that" and "would be willing to take whatever the top echelons take."

The president's annual salary is $200,000 a year; members of Congress earn $72,200 a year. The exact savings from such a pay cut are not known.

Dole and Michel said Reagan's $34 billion cut in domestic spending would raise protests, but could be passed. "When you get to the individual specifics, my Adam's apple was gurgitated, and I haven't swallowed it yet on a few of these items," Michel said. Dole, whose wife is Transportation Secretary Elizabeth Hanford Dole, cracked that "I kept hearing somebody next to me last night saying 'Amtrak' in er sleep."

Speakes said Reagan had told the congressional leaders that he is "willing to lead the charge -- to go to the people" on spending cuts, and reiterated his opposition to tax increases.

As in the past, there were protests against specific budget cuts yesterday. Boston Mayor Raymond Flynn (D) said the cuts in urban aid programs would be "devastating" and would "create a crisis of unemployment" in the nation's cities. "This proposed budget could topple most cities with the stroke of a pen," Flynn said.

Alan Beals, executive director of the National League of Cities, said the loss of general revenue-sharing "would mean major tax rises at the local level or major cutbacks in police and fire services."

He said that the Urban Development Action Grants program, which Reagan wants to eliminate, is "a good, solid Republican program with strong support from the private sector."