South African Prime Minister John Vorster, speaking with unmistakable derision about Carter administration policy in Africa, said yesterday that he differs profoundly with the cool U.S. response to the internal settlement in Rhodesia.

In an interview with The Washington Post, Vorster tersely underscored the sharp disagreements that have marked South Africa's relations with the United States over the past year.

He cited U.S. gestures toward what he called a dictatorship in Nigeria and U.S. failure to act in the Horn of Africa as elements of a policy that could destroy South Africa, which he termed "the one stable country in the sub-continent."

Vorster expressed for the first time South Africa's disagreement with the way the United States has responded to the establishment of a multi-racial interim government in Rhodesia.

"Where I differ profoundly with the U.S. was the lukewarm way in which they welcomed the internal settlement. I think they were wrong in taking up that attitude," he said.

Vorster's remak indicates that the mission to southern Africa last week by Secretary of State Cyrus Vance and British Foreign Secretary David Owen left unresolved U.S.-South African differences on Rhodesia. The prime minister refused, however, to discuss the substance of talks Vance and Owen held with South African officials in a stopover at Pretoria. The U.S. and Britian had hoped to arrange an "all-parties" conference on Rhodesia, including guerrilla groups opposed to the settlement, but did not succeed.

The vorster interview, held in his Parliamentary office in Capetown, reflected the enormous resentment of South Africa's white leadership toward the Carter administration.

Privately, other top officials spoke even more bluntly about the widening breach between South Africa and the United States, once this country's most important ally.

The Carter Administration's espousal of human rights and its decision to align itself with the aspirations of black Africa has increasingly put it in direct confrontation with a South African government intent on maintaining white minority rule over the country's economy and political system.

"Our differences are so deep and fundamental that the gap is unbridgeable," said one senior official, "All we can hope for is a modus vivendi, or a point at which relations won't deteriorate further.

"You genuinely, sincerely believthat whites are the villains and oppressors, and blacks are the have-nots and oppressed. Ergo, whites must govern," the official said.

But it is not merely U.S. criticism of South Africa's apartheid policy that is causing friction between the two countries. The latest irritants, as voiced by Vorster and others, were Carter's visit to Nigeria and Western positions in the talks on the future of Namibia, as well as the Rhodesia issue.

"There are ever so many African countries whose domestic policies are also very, very different from that of the United States . . . that have dictatorships, no press freedom or freedom of any kind, and apparently the U.S. government cooperates with these countries and has no quarrel with them. Nigeria is a case in point. But South Africa is condemned. So you can draw your own conclusion," said Vorster.

Other senior officials said that during his trip to Nigeria Carter had subordinated his concern for civil liberties to U.S. energy needs, because Nigeria is the second largest supplier of oil to the United States. Speaking generally of the administration's human rights campaign Vorster, said:

"It certainly is a very selective morality if there are any moral principles involved . . . Vance said in the case of the Phillipines that American security interests demanded that you overlook certain things. Well, that blows the whole bottom policy is such a high moral one."

Previous American administrations, while criticizing apartheid, had always maintained cordial ties to the Pretoria government. Vorster strongly suggested this is no longer the case, saying "It is clear to me that the present administration wants its internal policies should be."

On one issue, on which the United States and South Africa should be in close accord, the dangers inherent in the growing Soviet - Cuban presence on the continent, "It is a matter that perturbs me and should perturb each and every man concerned about peace in Africa," Vorster said.

But he derided U.S. declarations of alarm about Soviet-Cuban actions, mostly recently in the Horn of Africa. "At times it's very difficult to assess whether it's only words, as in the case of the Horn of Africa thing. I don't know that talking about it is going to put a stop to it. Certainly not when you are dealing with the Marxists," Vorster said.

Explaining why he felt the United States was now tilting so decidely toward black Africa, Vorster said, "It is perfectly clear to me that whereas in the last century you had a cramble for Africa to get physical control . . . now it is a question of crambling for the soul of Africa . . . for the votes and for the trade of Africa."

Vorster's manner towards his American visitors was polite but extremely cold. He broke off the session promptly at the end of the scheduled 30 minutes. Other top South African officials, however, lingered far longer with their American guests and were highly emotional in discussing the problems with the United States.

U.S. pressure on South Africa, said one official had become "counterproductive" because whites no longer believe that anything they can do to east dicrimination here - short of turning over control of the government to non-whites - will be enough for Washington.

"Nothing we do is good enough, and the end result is that people say "to hell with America, they want to destroy us," the official said.

This official and others said that modifications insuch areas as sports and theater seating, labelled as "cosmetic" by Americans and other Western officials, were actually major concessions by conservative South African.

Many South Africans plainly attribute the change in American attitudes towards them largely to President Carter's own convictions. "I get the feeling he wants to save my soul by burning me," one senior official remarked," and that he will pray while he is doing it."