South African President Frederik W. de Klerk yesterday brought his message of a new South Africa to audiences more skeptical than the one he had Monday at the White House, saying economic sanctions against his nation have been "counterproductive" and that Americans should understand that apartheid "is not an issue any longer."

In a day of media appearances, speeches and meetings with members of Congress, de Klerk declared South Africa will soon have a new constitution ensuring that no one race can dominate another.

Pressed to describe his vision of political power-sharing in the new South Africa, de Klerk accepted the concept of all votes as equal to each other. "I am quite happy to use one man, one vote," he said. He cited the "probability" that one common voters' roll, including the nation's 26 million blacks for the first time, will replace the current separate lists for the various races.

But de Klerk said the rights of minorities will be protected, and that South Africa will modify the Western democratic practice of naming a single strong president or prime minister as chief executive.

"We foresee a leadership situation where there will also be sharing of power in the executive, and not so much power concentrated in one man's hands," he told the National Press Club.

Some members of Congress said after meeting with de Klerk that they suspect he hopes such power-sharing will help to preserve a white veto over black decision-makers in the new government.

In discussing sanctions, de Klerk insisted that their imposition "to a great extent was counterproductive," and suggested he and President Bush did not discuss them at length because both understood that legal conditions for their removal "will be met" and that they will then be lifted.

"I want to say the political die is cast in South Africa," he said. "I can look America in the eye and say: We are no longer divided. . . . Apartheid is not an issue any longer. It is only kept alive by those who now have a vested interest in keeping it alive."

De Klerk thanked Bush for his declaration on Monday that the process of dismantling apartheid was "irreversible," a statement the South African leader said will aid in the process. Others yesterday questioned that declaration, and a spokesman for the African National Congress said the statement was "very worrisome for us" because it could be taken as a signal to lift sanctions by European and other nations not bound, as is the United States, by legislation.

"Removing sanctions," said the ANC's Patrick Lekota, "would leave us without anything to fall back on." He said the de Klerk government has left standing the "pillars" of apartheid, envisions a political power-sharing that will leave most power in white hands, and should not be treated as a nation "accepted in the world community."

Rep. William H. Gray III (D-Pa.) said Congress is more skeptical of de Klerk's progress than the Bush administration. "I think most members of Congress are not yet sure of where de Klerk is going in terms of change in South Africa," he said.

Rep. Howard Wolpe (D-Mich.), chairman of the House Foreign Affairs subcommittee on Africa and an author of the sanctions legislation, praised de Klerk's efforts but disagreed sharply with Bush on their reversibility.

"They are trying to assume a conclusion when there is no evidence of irreversibility. There is evidence of de Klerk's good intentions, but it is not at all clear he can deliver on his vision," Wolpe said.

Wolpe also said Bush, in pledging Monday that he would not "move the goal posts" by imposing new conditions before sanctions could be lifted, in fact was misstating some of the conditions now to make it easier to lift sanctions later.

One of the conditions is that South Africa "make substantial progress toward dismantling apartheid and establishing a non-racial democracy." That, he said, has not occurred.