President Reagan will address the nation on television next week to outline what he sees as the crisis in the economy but plans to withhold details of his new economic program until he delivers his State of the Union message in mid-February, Treasury Secretary Donald T. Regan said yesterday.

Both Regan and David Stockman, who was awaiting confirmation of his nomination as director of the Office of Management and Budget, told the Senate Appropriations Committee that while both tax and spending cuts were necessary the tax cuts were needed urgently and should not be delayed while Congress considered the spending cuts.

But Federal Reserve Chairman Paul Volcker quickly disagreed with the administration's new economic advisers, telling the same committee that spending cuts should come first.

Earlier, Regan outlined to reporters the basic tax proposal the White House will be sending Congress. He said the administration will propose a 10-percent-a-year cut in personal tax rates for three years, the proposal endorsed by Regan in the election campaign. Regan said the administration also would propose more generous depreciation rules for business. Other cuts, such as in the capital gains, tax, are unlikely to be part of the adminstration's package, he said.

"Gutsy decisions" on spending would go hand in hand with the tax cuts, Regan told a Senate panel later in the morning. But there is no need for a "dollar-for-dollar" reduction in spending, he said, adding "this tax program cannot wait until budget outlays are reduced."

Regan said the administration had two major goals: "a major reduction in inflation and a resurgence of economic growth." He promised a three-pronged approach to reduce spending and balance the budget, reduce "the oppressive tax rates on the American people" and "restore a stable monetary policy." Regan said people would be surprised at how big the administration's proposed budget cuts were.

He revised forward his earlier estimate of when the budget should be balanced, telling the Senate Appropriations Committee that the administration's intention was to balance it in two years, by fiscal 1984. At his confirmation hearing, he had said the budget might not be balanced until 1984.

Volcker emphasized the necessity of spending cuts in his testimony, somewhat contrasting with the stress on tax cuts given by Regan. "I would like to see final decisions on spending before we have tax cuts," Volcker told the panel, and he cautioned that "appraisals of the beneficial effects of tax reduction on economic growth, and therefore the revenue' feedback,' need to be realistic."

The Treasury secretary said that lower taxes would spur incentives and growth and encourage savings. As much as one-half or even two-thirds of the tax cut will be saved, he said.

Regan put much of the burden of fighting inflation onto the Fed, saying that "inflation is primarily a monetary phenomenon." Earlier he called for more stability in money growth.

Meanwhile, Stockman criticized the Fed for attempting to "stabilize rising interest rates through repeated liquidity injection in the spring and summer." In fact, interest rates were falling when the Fed injected reserves into the system last spring.

All three agreed that tight money policies, spending cuts and tax cuts should be implemented. Both Stockman and Regan promised a break with the economic policies of the past and in almost identical words pledged a return to "the clasical economic principles of sound budget policy and sound money." There was no longer a trade-off between inflation and unemployment, Regan said, as inflation "is a major cause of slow growth and unemployment."

He and stockman agreed that deep budget cuts must be made with no "sacred cows" such as defense, social programs, agricultural or business subsidies. Higher economic growth would help cut federal spending and the deficit, they said, but changes in entitlement programs also were needed.

"It may be proper to reexamine some of the concepts of unemployment on which many of our programs are based," Regan told the committee. He also repeated the administration view that students should not be entitled to Social Security payments.

Before the new administration took office, Stockman had been leading much of the economic policymaking. Regan, designated the adminstration's economic spokesman, said yesterday he expected Stockman to "return to a more traditional role" of guiding budget cuts through Congress.