S. Africa's 'last' leading black moderate despairs for black-white cooperation

All of South Africa's 30 million people are sharing an exquisitely warm Southern Hemisphere spring. But there is a political chill. From his remote tribal capital, black Zulu leader Gatsha Buthelezi sees political developments that are putting blacks and whites at cross-purposes.

In an interview, Buthelezi said South Africa's white minority appears ready to accept a bogus policy of ''reform'' that will have a decisive impact on black politics. He concedes the policy of moderation and negotiation he has long preached to blacks is on the verge of losing all credibility.

The ''reform'' that appears to be gaining acceptance by whites is a proposed new constitution drawn up by the ruling National Party. It breaks the color line by bringing two small nonwhite population groups - Indians and Coloreds (persons of mixed race descent) - into the now all-white Parliament.

But at the same time, the black majority will be constitutionally excluded from central government.

''Since 1910 (when South Africa became a union) we have struggled for inclusion,'' said Buthelezi. ''Once this door is slammed in our faces there will be a struggle for dismantling the state itself. I can see that confrontation politics becomes inevitable.''

Buthelezi is the last prominent black in South Africa to espouse moderate politics. Over the years, the government's white supremacist policies have radicalized the black political spectrum, making a conciliatory line almost impossible for blacks to embrace without being accused of ''selling out.''

Buthelezi's credibility has been badly dented at times. But he has performed a balancing act that is widely viwed as effective and earned a reputation among many whites as a black leader ''you can talk to'' while keeping a firm grip on his sizable political power base. He is chief minister of South Africa's Zulus, who at 6 million are the largest group - black or white - in the country.

Like most black leaders in South Africa, Buthelezi has concluded that the proposed constitution will polarize blacks further. He alone will bear the cost of the apparent failure of his policy of moderation and negotiation to achieve any concessions from the government.

Whites will vote on the constitution in a referendum in November. Already the tenor of the debate in white circles shows a fundamentally different perspective than that held by blacks. Whites tend to see the constitution as an important concession. Although some feel it does not go far enough, they attach importance to the fact that exclusive white rule would come to an end.

Blacks, on the other hand, see it as another act of deprivation. There is a deep feeling that a ''final door'' is being shut on any role for them in the central government. This time, as blacks see it, the white regime is seeking the help of other nonwhites to close the door.

Particularly distressing to Buthelezi is the fact that the constitution is predicated on the ''homelands'' policy, which blacks reject.

Over the years the government has sought to physically and politically isolate blacks into 10 separate tribal ''homelands.'' Pretoria hopes to push all the homelands to take ''independence'' - four have already done so - which statutorily excludes them from any rights in South Africa.

Pretoria's ultimate plan calls for a ''confederation of states,'' including South Africa and the ''independent'' black territories, similar to the European Community. But blacks have no intention of surrendering their claim to South Africa.

''Confederation is in the context of us accepting independence first,'' he says. ''But most blacks don't even want to go through the motions of independence. The whole idea horrifies us that we should be foreigners in our own country.''

Buthelezi remains a controversial figure in black politics because some blacks feel he is in a sense a collaborator on the homelands policy. He is chief minister of the KwaZulu homeland, using white-government resources to administer it.

Despite the warlike tradition of the Zulu, Buthelezi is staunchly against violence. As a young man, he was a member of the African National Congress and has never veered from its early strategy of nonviolence. The chances of blacks violently toppling the government are nil, he says.

The rise of the more radical ''black consciousness'' movement in the late 1960s helped characterize him as a moderate and eclipsed his importance in the eyes of many urban blacks. Despite his moderation, he has remained suspect by the government and one day in 1967 found police digging up his yard in search of arms.

Buthelezi's objection to the new constitution may block him from gaining a stronger urban footing. He had planned to put up candidates from Inkatha - the political group he founded which remains the largest black political organization here - in community council elections later this year in black townships. But he says now he will probably not participate.