DEMONSTRATIONS : ‘Mass Action’ Challenges S. Africa : Blacks’ campaign is viewed by De Klerk as a step toward violent overthrow of the government.

The African National Congress this month is hauling out the powerful weapon of “mass action”--protests, rallies, demonstrations, sit-ins, strikes and consumer boycotts--to wring concessions out of President Frederik W. de Klerk.

South Africa’s leaders can’t seem to agree on whether the looming street fight is the moral right of a voteless people, as the ANC contends, or the first step toward a violent overthrow of the government, as De Klerk contends.

Mass action would seem to be the very fiber of democratic expression, particularly for 29 million blacks with no access to the South African ballot box.

Yet De Klerk, his Cabinet ministers, the police and the liberal white business Establishment all are squealing loudly.

They say that mass action will whip up emotions, sowing more violence and intimidation in townships where law and order has all but disappeared. And they warn that strikes and boycotts will push the staggering economy off a cliff, frightening foreign investors and spawning even more black poverty.

“If this gets out of hand, any future government will inherit an economic wasteland,” warned Gerry Bezuidenhout, a spokesman for the South African Chamber of Business.

But the ANC and its impatient allies in the black trade unions say the protest campaign will lead to violence only if the government tries to stop it. They contend that it is the only peaceful avenue left to force the government to accept the inevitability of majority rule.

“Certainly the economy is going to be hurt,” said Jay Naidoo, general secretary of the Congress of South African Trade Unions, a 1-million-member alliance with close links to the ANC. “But sometimes you have to cut out the cancer to create a healthy body.”

The campaign already has begun with a variety of local strikes and boycotts, and a march is planned next week on the Union Buildings, the seat of government in Pretoria. It will grow in intensity with, among other things, a boycott of companies advertising their products on the state-run radio and television and sit-ins at government buildings.

The campaign is to culminate Aug. 3 with a strike, which could last as long as a week, making it the longest purely political walkout in the country’s history.

“We want to make clear that De Klerk cannot rule without our consent,” said Naidoo, whose organization is leading the effort. “This is the last signal to the government and big business that we are rapidly running out of patience.”

Such talk has given credibility to government claims that the ANC wants to use mass action to scuttle constitutional negotiations and force a black takeover of power.

At a funeral for victims of the Boipatong massacre, Naidoo warned that, if the government did not say uncle, “we will take them to hell with us,” a remark received with distress in the boardrooms of corporate South Africa.

While Naidoo is the fiery face of the movement, other leaders have taken a more moderate stance. ANC President Nelson Mandela denies that the ANC plans a takeover. Rather, he says, it is trying to shock the government into compromising on crucial constitutional issues, allowing the ANC to return to the negotiating table.

And business, union, sports and religious leaders are working behind the scenes to bridge the wide gap between the government and the ANC.

The government and the ANC made great strides in the negotiation process until talks stalled in mid-May. But, in their zest to show progress, they tended to paper over deep, philosophical differences, which have now emerged as a monkey wrench in the works.

In essence, the government wants a new constitution that will allow majority rule but will still give the white minority, outnumbered by blacks 5 to 1, a veto over measures that affect them. The ANC favors a system in which the majority prevails and minorities are protected by a bill of rights and an independent judiciary.

But confrontation in the streets is a risky venture all around. The government must maintain order while not appearing to be curtailing free expression. And, with the clock running, it must lure the ANC back to the table without sacrificing the concerns of its own constituents.

The ANC, though, may find the streets a dangerous, unpredictable arena. It will be hard-pressed to maintain nationwide protests without triggering violence, which could cost it international support and undermine its negotiating position.

But if the ANC gives in too easily, it risks losing large chunks of its supporters. And they are as restless, angry and distrustful of the white government as they’ve ever been.