South African Foreign Minister Roleof "Pik" Botha declared in Johannesburg yesterday that the basis for the Carter Administration's decision to support a mandatory arms embargo against his country was "totally unacceptable."

"If the maintenance of human rights was indeed the concern of the American government, America should be pressing for sanctions against more than half the governments in the world," Botha said.

The minister said he felt that South Africa had been "singled out for special treatment" because of a "vendetta" against it by a number of countries.

In Washington, South African officials said that while a mandatory arms embargo would a "grave" step, it "would not bring South Africa to its knees."

Carl F. Noffke, head of the South African Information Service, said his country already manufactures 75 per cent of its military weapons and can easily produce the remaining 25 per cent if necessary.

Any type of mandatory arms embargo "will stimulate greater industrial activity in South Africa" as has been the case with previous voluntary arms embargoes, and may even "spark the greatest economic boom in South Africa," Noffke said.

An arms embargo has been expected by the South African government for almost two decades, Noffke said, adding that the government "has prepared the South African people for what is ahead."

He predicted that an arms embargo would not convince the South African government to relent on its crackdown on dissidents last week, but rather would "strengthen the bond between whites as well as between blacks and whites in South Africa."