Secretary of State George P. Shultz said today the Reagan administration is prepared to use "pressure" to combat apartheid in South Africa but charged that the current sanctions drive in Congress would sap this effort by mandating U.S. "withdrawal" instead.

He called the present state of emergency and drastic clampdown in South Africa "a major backward step." He added, "I hope it doesn't lead to a feeling of hopelessness, that all there is left is confrontation and not dialogue."

Shultz, on the first leg of an eight-day trip to Asia and the Pacific, spoke at length, however, against the House vote Wednesday to order total and immediate U.S. disinvestment from South Africa.

Shultz declared that U.S. policy is "to bring about change through a combination of pressure and persuasion," but that a key tactical consideration is "husbanding" available U.S. clout to exert it most effectively.

Shultz did not spell out what pressures the administration might apply against Pretoria if given a reprieve by the Senate from the disinvestment policy ordered by the House. Other officials indicated the administration may use the several months before Senate action to seek to persuade South Africa, through a carrot-and-stick approach, to modify apartheid.

Shultz said that "it isn't a question of whether to have pressure or not. Pressure is always good there. The question is what kind and how to use it."

Shultz, who in the past criticized economic sanctions as "light-switch diplomacy" which is turned on and off ineffectively, said pressures against South Africa should be adjusted gradually like a rheostat, or light dimmer.

As an example of pressure he approves, Shultz mentioned the U.S. expulsion early this month of the senior South African military attache in Washington as a gesture of disapproval after Pretoria's raids against neighboring countries.

If the disinvestment legislation becomes law, Shultz said, "we wouldn't be there any more" and all that would be left to the United States would be military action, "which we're not contemplating and I don't think we should contemplate."

Regarding U.S.-Soviet relations, Shultz told reporters aboard his plane he believes the Soviet leaders will "take into account" President Reagan's Glassboro, N.J., speech in deciding whether to move ahead this summer with planning sessions for the next U.S.-Soviet summit.

Reagan's address, which was widely seen as an abrupt shift from his tough anti-Soviet rhetoric and actions of recent weeks, was "very consistent" with his past positions, according to Shultz. He said this is because the president, while "tough-minded," is "always willing to recognize fresh developments" such as what Shultz called the "serious proposals" recently made by Moscow in the Geneva arms negotiations.

Shultz would not predict how Moscow will act on the U.S. suggestion that he and Soviet Foreign Minister Eduard Shevardnadze meet in Europe to restart summit planning.

Shultz revealed that the reason for suggesting Europe was that the Soviets passed word that, "for reasons best known to them," they preferred that Shevardnadze not come to the United States at this time.