RUST DE WINTER, SOUTH AFRICA -- Kobus Germishuys is a deliberative man. He puffed on his pipe as he considered the question, then tapped it out against his palm before answering. "If there is an agreement that will lead to a black government," the white 47-year-old sheep farmer said in a mild voice, "then I will sabotage it in any way I can."

It would make no difference, Germishuys added, if the new black government turned out to be conciliatory, if it left white farmers alone to get on with their lives. To him, the very idea of blacks governing South Africa is unacceptable.

Nor would it make any difference if the new constitution were approved in a whites-only referendum, which is what President Frederik W. de Klerk has pledged to hold before implementing any agreement reached in current negotiations with South Africa's black nationalists.

"I will still not accept it," Germishuys insisted. "Look, I am prepared to have a black neighbor farming next door to me -- provided, of course, he is the type who will honor the gentlemen's agreements that a farmer always has with his neighbors. But a black government is different. This is our country; our ancestors fought and died for it, and it must be governed by our people."

Germishuys, who lives near the village of Rust de Winter in the bushveld plains of the northeastern province of Transvaal, was asked about his reference to sabotage. Did he mean he would join an armed revolt against the de Klerk government if it reaches an agreement with Nelson Mandela and his African National Congress?

"Well, no," Germishuys replied slowly. "I am not a man for bombs. I would have to find other ways. Sabotage can take many forms, right down to refusing to pay one's income tax."

"But I believe there will be war, and I have a measure of sympathy for those who will go to such lengths," he added.

Germishuys's response to the negotiating process underway between de Klerk and the ANC, South Africa's most prominent black nationalist group, is not unusual in this region. In two days of conversations with white farmers in northern Transvaal, only one expressed support for the negotiations and said he would be prepared to live under a black government.

Asked how many other white farmers he knew who shared his open-minded views, Dirk van Deventer replied, "None."

This is South Africa's "Deep North," where the most disputatious spirits among the Dutchdescended Afrikaner pioneers trekked farthest in their ox wagons during the early 19th century. They fought off black tribes as they thrust northward into the interior to escape British colonial rule over the southern part of the country and what they regarded as the tyranny of a neighbor close enough for his chimney smoke to be visible.

This part of the country has always been fiercely individualistic and racially divided. Today, it forms the heartland of Andries Treurnicht's far-right Conservative Party.

There has been a growing threat of terrorist violence by white extremists since de Klerk legalized the ANC last February, released Mandela from 27 years in prison and began preliminary talks with him about a new constitution to replace the country's apartheid system of racial separation.

Wim Booyse, a risk analyst specializing assessing the right-wing threat, has compiled a list of 70 rightist groups that have sprung up, including eight paramilitary forces and 28 smaller terrorist units, some consisting of little more than two-man or four-man cells. Overall, Booyse estimates there are about 550 white extremists ready to engage in terrorist activities.

What do ordinary Afrikaners feel about those extremists? The conversations with the white farmers of the northern Transvaal indicate that at least in this tough region, there is extensive popular support for them.

"I don't think the government realizes how widespread the resistance is to what it is doing," said Willem Lewis, a prominent farmer in the Ellisras district near the Botswana border. Lewis is vice president of the Transvaal Agricultural Union and travels the region continually.

"There is a tremendous feeling building up, even among people who still want to be loyal to de Klerk's National Party," Lewis said.

"There is a broad movement at grass-roots level of people arming themselves," he continued. "The day it comes to the negotiating table and people feel that their land and their future are being given away, then I must be honest and say that I will declare war."

Jan Fourie is an army general who retired eight years ago and now farms near Warmbaths, west of here. "We Afrikaners are not impulsive," said Fourie. "We are not like the hotblooded Latins. Afrikaners will take and take, up to a final stress point where they will not take it anymore. Then they will fight."

"I don't know what that point is, but when it comes, there will be an insurrection and a tremendous number of police and army people will join in," said Fourie, who once trained special units in irregular warfare and headed the tough Parachute Battalion.

As for what an uprising could achieve, Germishuys said: "My children will have no future anyway, so what difference does it make?"