THE SOWETO RIOTS removed from all but the thickest South African minds the assumption that the country's ruling white minority could somehow tough it out with its black majority without far-reaching change. But a year later, as black desperation and resistance grows, it remains a question whether the pace of the change acceptable to the governing whites is sufficient to produce a tolerably nonviolent racial accommodation. The question is central, we submit, not only to South Africans but to Americans. For American policy, as it now seems to be developing, rests on the premise that within South Africa there is insufficient move and momentum for change and that, therefore, pressure must be applied by the United States.

How does one judge? The police banned the all-white, liberal, English-speaking Witwatersrand University from inviting white and black moderates to speak at a Soweto anniversary rally on grounds that it was "not in the best interest" for white students to act in sympathy with blacks. Meanwhile, the all-white, conservative, Afrikaans-speaking Stellenbosch University has decided to admit its first black students.

The basic legal structure of white domination is untouched, but the business community is moving against some aspects of economic discrimination. Black leaders continue to be "banned" and black political expressions censored. But one government minister won a by-election declaring he would die for his country but not for signs in an elevator, and another proposed a political transformation bestowing rights even on urban blacks, of this extraordinary proposal the prime minister said merely that it was "not practical politics at this stage."

Gun purchases and secret exports of private funds by whites are said to be mounting. So are reports that within the innermost councils of power in white South Africa, deliberations aimed at climactic changes of power and policy are being seriously pursued.

Frankly, we do not feel we are in a position to make the judgement that meaningful racial change is still so remote and unthinkable in South Africa that the United States must threaten Pretoria with punitive political action in order to promote it. But - and here is our main anxiety - we are not convinced that he Carter administration is in such a position either. To express the moral aspirations of Americans for racial justice, to demonstrate to other Africans that the United States abhors racism: These are necessary and useful things to do. But is the United States otherwise contributing to a solution in South Africa, or merely increasing polarization and gratuitously raising expectations there? Perhaps some better idea of the answer to that question will emerge from a comprehensive statement of the administration's African policy, which is said to be in preparation. We hope so, for a clear and cogent explanation of exactly what hthe President is up to in Africa, in general, and in South Africa, in particular, is overdue.