Senior-citizen groups are gearing up to block any attempt to cut Social Security benefits as part of a deficit-cutting deal between the White House and Congress.

Benefit cuts were on the bargaining table last week when the talks recessed for the Fourth of July congressional recess. The question is whether the issue will be raised next week when negotiators return.

"There is a lot of aim-taking, but the question is whether anyone is going to pull the trigger," said John Rother, lobbyist for the American Association of Retired Persons (AARP).

In hopes of turning the negotiators' sights elsewhere, senior-citizen groups are planning letter-writing campaigns and contemplating demonstrations.

The political risks in reducing Social Security benefits have made the program one of the budget's untouchables. The elderly are one of the biggest and best organized blocs in the nation -- and, more important, one that regularly votes in large numbers.

In this election year that fact has not eluded lawmakers of either party.

"Frankly, I don't think you have to touch cost-of-living increases {in Social Security benefits} to solve this budget deficit," said Sen. Pete V. Domenici (N.M.), the ranking Republican on the Senate Budget Committee.

"You can talk about it," said Senate Budget Committee Chairman Jim Sasser (D-Tenn.), "but, in my judgment, that's not going to happen."

Some Democratic political professionals do not think their party's lawmakers should even talk about it.

"The two things the voters still give us credit for is standing up for the middle class and protecting Social Security," said Harrison Hickman, a Democratic poll taker. "This is the time we can really communicate that we will uphold our promises. Just because the president breaks his doesn't mean we have to break ours."

But others do not rule it out in the name of deficit-reduction and fairness.

"Entitlements are going to have to take a pretty good shot if you're going to reach $50 billion," the bargainers' target for fiscal 1991 deficit reduction, said Rep. Bill Frenzel (Minn.), the House Budget Committee's ranking GOP member. "And you can't hurt one crowd and leave others untouched."

But senior-citizen groups remain reluctant to concede the need for any change in Social Security, noting that the Social Security trust fund is running a surplus and is not responsible for the deficit.

"There has been tremendous unevenness about what caused the deficit, and there should be tremendous unevenness about how to solve it," said Ron Pollack, executive director of Families USA, an advocacy group for the elderly. "Should seniors contribute to solving the deficit? In the abstract, yes. But . . . it hasn't been the elderly or lower-income people who have benefited from tax cuts."

Senior-citizen groups are particularly adamant in their opposition to cuts in the annual cost-of-living adjustments in Social Security benefits, called COLAs. "Our main message is: keep your hands off the COLA," Pollack said.

Budget negotiators have discussed a permanent three-month delay in Social Security cost-of-living adjustments. That would save $3.3 billion in the first year and $17 billion over five years, according to congressional projections.

The average monthly Social Security benefit for retirees is $567, according to the Social Security Administration. A cut in inflation adjustments, said AARP's Rother, would be "a heavy hit for someone at that income level."

Robert Greenstein, director of the Center on Budget and Policy Priorities, estimated that a cut in cost-of-living adjustments would hit lower-income retirees harder than higher-income retirees. "It is highly regressive," he said.

As an alternative to a cut, bargainers also discussed ways of getting more tax revenues from Social Security beneficiaries.

Currently, couples with a taxable income of more than $32,000 a year and individuals with a taxable annual income of more than $25,000 must pay taxes on 50 percent of their benefits. Taxing 85 percent of the benefits instead would generate an additional $1.1 billion the first year and $20 billion over five years, according to the Congressional Budget Office.

Moreover, it would be a far more progressive way of raising money. Virtually all the Social Security recipients who would pay more under this change would be among the wealthiest one-fifth of taxpayers.

Taxing Social Security benefits in that way also would bring their tax treatment in line with that of private pension benefits. The government taxes pension payments made in excess of a retiree's contributions to the plan.

AARP's Rother said that increasing taxes on Social Security benefits would be "a stronger candidate" than cutting inflation adjustments.

"It's easier to sell politically," said William Schneider, an American Enterprise Institute resident fellow. "It affects a small number of people who are high-income. Cost-of-living adjustments affect everybody."

But it is precisely those high-income elderly who pressured Congress last year to kill the expansion of Medicare to cover catastrophic illnesses. As a result, even though many policy analysts agree that taxing Social Security benefits makes sense, few expect it to become part of a budget pact.

Few lawmakers can forget the political firestorm over coverage for catastrophic illness -- or the earlier battles over Social Security.

In 1985, Senate Republicans crawled out on a political limb by approving a budget -- with then-Vice President George Bush casting the deciding vote -- that would have eliminated one year's Social Security cost-of-living increase. Two months later, President Ronald Reagan sat with then-House Speaker Thomas P. O'Neill Jr. (D-Mass.) beneath an oak tree on the White House lawn and sawed the limb off, killing the deal and putting Social Security off limits.

In 1987, White House and congressional budget negotiators were close to a deal cutting one year's Social Security cost-of-living adjustments in half. But the accord fell apart when then-Treasury Secretary James A. Baker III would not go along with a comparable reduction in tax cuts, most of them benefiting the wealthy.

"We couldn't agree on the equitable share of the burden," recalled House Speaker Thomas S. Foley (D-Wash.), who, as House majority leader, presided over those talks.

The issue of equity and fairness will again dominate talks about Social Security and the entire deficit-reduction negotiations.

"We've always acknowledged that older people have to share in sacrifice," said AARP's Rother, "but we aren't prepared to see lower-income elderly shoulder a disproportionate share."