President Reagan is likely to compromise on his fiscal 1983 budget only if Congress stops talking about tax increases and comes up with a "significantly better" plan than his for spending cuts, Senate Budget Committee Chairman Pete V. Domenici (R-N.M.) said yesterday.

"I think only that way" will Reagan agree to a bipartisan budget compromise, Domenici said in suggesting a new strategy for breaking down Reagan's resistance to congressional tampering with his budget.

Tax increases have been a major part of all budget alternatives proposed so far in Congress, including one from Domenici, and Democrats especially have tended to emphasize them over cuts in spending programs that were already squeezed by Congress last year.

Just before Domenici outlined the possible new strategy on "Meet the Press" (NBC, WRC), former vice president Walter F. Mondale called for major revision of the president's tax program, including repeal of the scheduled 1983 income tax cut, a speed-up of the one scheduled for this year and repeal of the "leasing" provisions voted last year under which corporations can buy and sell their tax breaks.

Mondale was interviewed on "Face the Nation" (CBS, WDVM), during which he also accused the Reagan administration of making "the greatest and most colossal economic mistakes in history."

Domenici did not rule out tax increases as part of negotiations with the president but simply said they should be set aside while congressional leaders are trying to get the president to the bargaining table.

"I believe the most important thing for a bipartisan group in the Senate to do is to forget about taxes for a minute, set it aside, put down what we collectively say we will do in budget restraint over the next three years, credible notions that will build a package of restraint . . . ," Domenici said.

"If that is no better than the president's, then forget about it," Domenici continued. "If it's significantly better than the president's, then I think you begin to have some negotiating room."

Domenici did not say bigger cuts, only "better" ones, apparently meaning savings from entitlement programs that guarantee benefits from year to year to all who qualify rather than payments that are dependent on annual appropriations.

Domenici's plan calls for eliminating cost-of-living increases for Social Security, Medicare, Medicaid and other inflation-indexed entitlements for fiscal 1983, which he said add up to about twice the entitlement savings that Reagan proposed.

Domenici also is urging only about half as much in the way of domestic appropriations savings as Reagan did.

Whether Reagan would talk about taxincreases if Congress first came up with "better" spending cuts in unclear.

But White House aides, who have been wrong before in predicting Reagan's intentions on taxes, have said he might consider selective tax increases--although not a rollback in his 10 percent across-the-board tax cuts for 1982 and 1983--if entitlement program cuts were nailed down in advance.

"The president's concern is my concern, that we will look first to raising taxes instead of first looking to this enormous budget that even after the president's proposed cuts is growing dramatically," Domenici said.

Meanwhile, Office of Management and Budget Director David A. Stockman formally informed the congressional Budget committees that farm price support costs will be $4.9 billion higher than the $1.8 billion level that Reagan anticipated in his fiscal 1983 budget in January.

This, in effect, confirms more up-to-date figures from the Congressional Budget Office.

Although CBO officials said the administration was not changing its official deficit projection of $91.5 billion for fiscal 1983, the additional farm costs, stemming from price increases and crop estimates, would push the deficit higher if the additional costs materialize. CBO forecasts a deficit of about $121 billion under Reagan's program.