WITH ITS SUDDEN, COMPREHENSIVE CRACKDOWN on moderate black and interracial organizations and press three weeks ago, South Africa's white minority regime has made it more than clear that it is not about to reform its apartheid policy in any meaningful way, let alone accept any move toward a black majority government in the future. Last month's wave of repression was the harshest and widest-ranging since the early '60s: the regime banned 18--or virtually all--of the country's black organizations and shut down South Africa's leading black newspapers, thus openly betraying its claim that South Africa allows the freest press is Africa.

South African Prime Minister John Vorster has defended the bannings by contending that the outlawed organizations posed a major threat to state security. This argument is not only callous but preposterous, given that the government has restricted the activities of these organizations for years, through continual security police harrassment and routine detention and banning of the groups' leaders.

The stepped-up repression seems rather to be an attempt to further ensure that the country's voting white minority will hand Vorster an overwhelming victory in the general elections later this month, and to serve notice to the U.S. and other Western powers that the white minority is prepared to fight to the last to retain its social predominance and political power.

In the face of this increasingly evident intransigence, the Carter administration's response thus far has been overly cautious, if not to say timid. Although symbolically significant, the U.S. agreement in the United Nations last week to a mandatory embargo on all military sales to the Vorster regime does not substantially alter America's official posture, which for over a decade has been voluntary refusal to deal arms to South Africa. The U.S. decision, meanwhile, to use its Security Council veto to block proposals for equivalent embargoes on trade and investment suggests that the Carter administration still holds out hope for bringing an end to the white government's apartheid policies from within. Yet there would now seem to be more than enough evidence that any such faith is misplaced.

Having opposed the mandatory investment embargo, the administration should now at least actively encourage major corporations that do business in South Africa to disinvest. More important, the U.S. should seek to expand its dialogue with black South African nationalists who are fighting for majority rule. For if this most recent crackdown only makes it appear more likely that the white minority and the black majority are headed for an all-out struggle for political power in South Africa--as even white South African liberals who favor peaceful reform now predict--the U.S. should be in a position to support the fight for black majority rule, rather than continuing to underwrite the defiant policies of Vorster's minority regime.