The case for United States investment in South Africa as a tool for encouraging progressive change is stronger than ever. So says Harry Oppenheimer, this country's most prominent industrialist and the man who more than any other controls the gold, diamonds, platinum, uranium, and other commodities that make South Africa a minerals superpower.
Watching with concern the new push in the US for reducing economic ties with South Africa, Oppenheimer said in an interview that while such efforts were ''well-meaning'' they were ''quite a foolish approach.''
''Insofar as there is change and there is hope in South Africa, (the change) really is happening because of the pressure which has been brought on the politics of the country by the growth of the economy,'' he maintains.
More than ever before, Oppenheimer sees evidence that economic forces are bringing ''big changes'' for South Africa's black majority. But he is quick to add that in the area of political rights, ''there hasn't been something meaningful'' for blacks.
Oppenheimer is the quintessential symbol of South Africa's English-dominated business community and its traditional opposition to the Afrikaner government.
For a quarter of a century, Harry Oppenheimer was chairman of the Anglo American Corporation, South Africa's largest mining conglomerate. Although he retired from the board last year, he still effectively controls the company. Although Oppenheimer left opposition politics in 1957, he remained an outspoken and influential liberal critic of the government's apartheid policies.
But as a capitalist and a supporter of foreign investment in South Africa, Oppenheimer is regarded with deep skepticism by segments of the black population. Many see him as a vital prop to the perpetuation of the existing social structure in South Africa.
The areas where Oppenheimer sees clear advancement for blacks:
* Black bargaining power is increasing dramatically thanks to a fundamental redistribution of wealth from whites to blacks. He estimates that black income as a proportion of overall personal income has gone from 25 percent a decade ago to 40 percent today.
* Blacks are now acknowledged by the government to be ''permanent'' residents in the ''white'' urban areas. The hope that someday blacks would leave urban areas and return to their tribal ''homelands'' has been abandoned by the government.
* Acknowledging the permanence of blacks has forced the government to give them more rights in urban areas and better amenities. And black urban townships are being granted more rights to govern.
* Full trade-union rights have been extended to black workers. The unionization of blacks has ''produced black controlled organizations . . . that are certain to be used for political objectives.''
All of these changes, in Oppenheimer's view, contribute to produce a healthy economy. Prosperity also ''produces an atmosphere where change is more acceptable to whites,'' he said.
Most of these changes may be called ''too little, too late'' by blacks. But Oppenheimer insists that in the economic sphere, ''if you're prepared to think of five or 10 years ago, things have changed out of all recognition.''