S. Africa's black leaders near showdown over how to win control. At issue is whether negotiation with Botha regime still possible

Rival black leaders have begun girding for a showdown over how to win power from the country's white-minority government. The contest burst into the open most recently, during rival May Day demonstrations. At issue is whether there remains room for compromise with the ruling party of President Pieter W. Botha, which has announced a strategy congress for August.

The chief black advocate of compromise, Zulu leader Gatsha Buthelezi, drew some 60,000 backers for a May Day rally in the Indian Ocean city of Durban. But an estimated 1.5 million black workers were meanwhile mounting the country's largest-ever work stoppage to press for a quicker and more far-reaching devolution of power.

Chief Buthelezi is pinning his hopes on one-month-old talks with the province of Natal, which borders his own territory of KwaZulu and is ruled by more moderate white politicians than those in the national government.

The talks' aim is to agree on guidelines for a joint legislature.

Although the talks have been held behind closed doors, the Monitor has learned that considerable progress has been made toward a draft charter. It would give the 75-percent Zulu majority in the Natal-KwaZulu region a dominant voice in the shared legislature and probably make Buthelezi the area's ``prime minister.''

Conference sources say final agreement seems at least a month away but that delegates have narrowed differences on a compromise. This would award a disproportionate share of seats to whites and other minorities, and require a two-thirds parliamentary majority on selected issues -- essentially a white veto on such questions.

But for Buthelezi, the talks' achievement so far may prove the easy part. He has yet to secure assurances of President Botha's support for such a compromise, crucial to its required approval by the national Parliament. Nor has the chief managed to dampen growing opposition from more radical black leaders.

This was a major point of his May Day rally, nominally called to launch a black labor union to rival the federation that mounted the unprecedented nationwide work stoppage. ``I wish I could send a video of it to Oliver Tambo,'' Buthelezi remarked in an interview. The reference was to the leader-in-exile of the outlawed African National Congress.

The ANC, the black Congress of South African Trade Unions, Anglican Bishop Desmond Tutu, and other black leaders have rejected Buthelezi's approach as out of sync with the anti-apartheid violence that has ravaged South Africa for the past 20 months.

They say Botha's government must abandon its strategy to ``reform'' the country's apartheid system of race segregation.

Apartheid, say these groups and leaders, must be scrapped wholesale. South African troops, introduced into black areas during the violence, must be withdrawn. Also demanded is the lifting of political restrictions -- such as the imprisonment of early ANC leader Nelson Mandela -- and the outlawing of ANC membership or activity inside South Africa.

One of Buthelezi's most prominent black critics remarked in an interview over the weekend that the chief had failed to realize the ``disappearance of the middle ground'' in the teeming black urban townships where much of the recent violence has occurred.

``Anyone who cooperates at all with the existing system is finished,'' the critic said. He argued that, even if the Botha government did decide to meet Buthelezi halfway, it risked ``dealing with a man who represents no constituency.''

Botha's own plans remain secret. He has two party representatives as ``observers'' in the Durban negotiations. But amid growing pressure from his own right flank, he has stopped short of endorsing the idea of a multiracial parliament for the region.

Botha has called a National Party Congress -- one of only several in recent decades -- for August. He is expected to use it to unveil specifics of proposals to give at least a consultative role to blacks. Some South African newspapers have speculated he may even try to bring one or more blacks into his Cabinet.

Buthelezi indicated such steps would be insufficient -- unless accompanied by a scrapping of all one-race government structures, the release of Mr. Mandela, and the lifting of restrictions on other leaders and groups. He added that each time Botha shrugged off such changes, the government in effect ``pulls the rug out from under me'' and encourages more radical black demands.

Buthelezi declined to comment on chances Botha would back the so-called ``KwaNatal'' regional compromise. But a prominent Buthelezi ally was less circumspect: ``Botha should realize, if he's interested in peaceful change, that this may be a last chance.''