Hope in Southern Africa?

WHEN a white politician sits down with an imprisoned black man to talk, that might not seem like much of an event in most of the world. But when the meeting takes place in apartheid-riven South Africa; when the white politician is one of the leaders of Afrikaner nationalism; and when the black man is Nelson Mandela, the head of the African National Congress (ANC), jailed for 27 years for challenging white supremacy, that is an event of considerable drama.

It was South Africa's President P.W. Botha himself who invited Mr. Mandela to come from his place of detention in Cape Town to visit for 45 minutes at the presidential residence.

The two men had never met before, and it was the first time Mandela had ever met a white official of such seniority.

The lack of such communication between black and white leaders over the years is in itself a tragic demonstration of wasted opportunity. The fact that such a meeting has at last taken place is a gleam of hope for the future.

A government announcement said that President Botha and Mandela had confirmed ``their support for peaceful development in South Africa.''

In the subtle political language of South Africa, that could be significant stuff. It could give the government the political fig leaf it is looking for to release Mandela. The government has said Mandela must disavow the violence of the ANC's militant wing before he can be freed.

The African National Congress, meanwhile, has said Mandela must be released, and other conditions fulfilled, before it would suspend its guerrilla war against South Africa's white government.

Mandela's long imprisonment has become an embarrassment to the South African government, and especially so to a new generation of government party leaders. Some members of the cabinet have been lobbying for Mandela's release.

National Party leader F.W. de Klerk, who is expected to succeed Mr. Botha as President later this year, is being looked to for signs of any new flexibility in handling South Africa's problems.

Mr. de Klerk is faced, on the one hand, by white conservatives who want no dilution of apartheid, the policy of racial segregation which has earned South Africa opprobrium around the world.

But, on the other hand, he is confronted by pressure from leaders in Western Europe, from whence he has just returned, as well as the United States, not only to release Mandela but to move in the direction of accommodation with South Africa's black majority.

There are other new factors in play as well. There is the erosion of tension between the United States and the Soviet Union - an improvement in relations that is having an impact on the African continent. The Soviets have been constructive in encouraging the withdrawal of Cuban troops from Angola. That in turn has led to the withdrawal of South African troops from Angola. Peace is coming to Angola and independence to South African-ruled Namibia.

It has taken a long time for the winds of change to gather momentum in southern Africa, but they are blowing at last throughout the region and may riffle across the very bastion of apartheid, South Africa itself.

Of course, Nelson Mandela went back to his place of detention after his chat with the South African president. But the meeting has certainly enhanced his stature, and that of the ANC. His release may now be only a matter of time.

Within this framework the ANC, although officially banned in South Africa, seems to be speaking to the white regime in more conciliatory terms. It seems to find Mr. de Klerk more promising than previous government leaders.

Hopes have been raised, and dashed, in South Africa before. It is much too early to suggest that the dreadful racial confrontation which has beset that rich and beautiful country is nearing its end. But a dramatic face-to-face between black and white leaders who have never met before leaves one hoping again.