Senate Finance Committee Chairman Robert J. Dole (R-Kan.), reflecting increasing congressional qualms over budget deficit projections, suggested yesterday that Congress might elect to substitute faster tax indexing for the last year of President Reagan's three-year tax cut.

Reagan has repeatedly refused to consider any watering down of his tax-cut legislation, but Dole, in an appearance on "Face the Nation" (CBS, WDVM), said it "must be assumed" that the president will have to accept some effort to increase revenues and reduce the increasing budget deficit.

"It would seem to me . . . that he knows that sooner or later there's going to be an arrangement or an accommodation," Dole said.

The 1981 tax legislation provided for taxes to be tied to an inflation index, beginning in 1985, as a way of avoiding "bracket creep." The same legislative package calls for 25 percent in cuts over a three-year period. But Dole said he would prefer to move indexing ahead 18 months.

"By advancing indexing to July 1, 1983, eliminating the 10 precent cut . . . you would save $20 billion in two years," said Dole, who, along with 10 other Republicans on the finance panel, will get a chance to present their views on the budget in a meeting with Reagan today.

Dole also suggested the need for "adjustments" in the automatic cost-of-living increases in Social Security benefits and other entitlement programs as a way to hold down expenditures--a proposal that was echoed by House Budget Committee Chairman James R. Jones (D-Okla.) in a speech yesterday to mayors and city council members at the convention of the National League of Cities here.

Jones, who also favored delaying the 1983 tax cut, described the entitlement programs as "a political hot potato," but said, "We've got to reduce the growth."

However, another majority member of the Senate Finance Committee, William L. Armstrong (R-Colo.), claimed that Congress would find a way to reduce the administration's looming budget deficit without cutting or delaying the third year of the tax cut.

"The supply-siders, and I'm one of them, are going to really put their shoulder to the wheel on the budget-cutting side in order to protect the tax cut," Armstrong said on "Newsmaker Sunday" (Cable News Network).

Dole noted that there are a number of different proposals for limiting the growth of entitlement programs, including the imposition of a freeze on Social Security benefits and others. While this is an election year, Dole said Congress must do something about cost-of-living adjustments to entitlements that are helping to make those programs so costly.

"If we're really serious about bringing down deficits and not just posturing and making political speeches, we have to," Dole said.

Last week, Office of Management and Budget Director David A. Stockman told a congressional panel that a freeze on cost-of-living increases in entitlement progams "may be warranted . . . as a temporary expedient" to help reduce budget deficits.

Stockman testified that cost-of-living increases for entitlement programs would cost $24.9 billion in fiscal 1983, including $16.3 billion for Social Security alone.

Jones, in his speech yesterday, also said there is a "growing bipartisan consensus" for curbing defense spending, and Dole gave notice that he expected defense to share in the budget cutting.

"We want Defense Secretary Casper W. Weinberger to get out his knife. I mean he has a reputation, 'Cap the Knife,' " Dole said. "If we're going to have this balanced package again, we can't leave defense out . . . . If we're talking about reaching an agreement, everyone has to give, including the president."

Reagan has been firm on resisting cuts in his defense budget, as well, but Dole said the president had overlooked one point: "You know, he's worth $10 or $20 billion in defense just to have him rambling around the White House. He's worth a weapons system or two."