The South African government announced last night that effective Friday it would have the authority to force foreign companies operating in South Africa to produce strategic materials.

Economic Affairs Minister Chris Heunis, in a speech in Durban, South Africa, stressed that the move was "only an enabling measure" and expressed the hope he would not have to invoke the act "in more that isolated cases."

Heunis also declared that the South African government's objective was "not in the first place, or even as an important consideration, aimed at the manufacturing of arms."

Nevertheless, the legislation authorizing the government to assume these powers was passed in 1970, and U.S. officials indicated a belief that it was no coincidence that Preteria decided to grant itself this authority only five days after the U.N. Security Council imposed a mendatory arms embargo on South Africa.

"Well certainly have to study this," one U.S. official said.

South African officials last night said they were unable to elaborate what type of goods might fall under the category strategic materials.

Heunis, in his speech, said only that the measure would insure the supply of goods that are deemed "necessary or expedient in the interest of the safety of the state." He said the legislation provides for compensation to foreign corporations for demands made on them by the government.

In Pretoria, Justice Minister James Kruger accused President Carter yesterday of applying "double standards" and vowed that South Africa would not bow under international pressure.

"We'll be damned if we go over to one man, one vote, ever," Kruger told reporters.

Foreign Minister Roelof Botha, meanwhile, called U.S. Ambassador to the United Nations Andrew Young a "a racialist" who hates Americans for what "they had done to his forefathers as slaves."

Speaking at an election rally 75 miles south of Durban, Botha asked. "Must I pay the price for Mr. Young's hatred of white Americans?"

During his meeting with reports, Kruger also admitted that black nationalist Steve Biko died of brain injuries while in police custody, but insisted there was no police involvement "as far as I know."

A man can damage his brain in many ways," Kruger said. Asked whether the medical findings in the case of the 30-year-old Biko, whose death in a Pretoria prison cell touched off an international furor, were compatible with self-inflicted wounds, Kruger replied.

"I don't know if they were self-inflicted. But I often think of banging my own head against a wall."