Five weeks after success at Camp David transformed the U.S. role in the Middle East, the Carter administration has quietly altered another key component of its foreign policy by offering to give South Africa's white minority govenment a more sympathetic hearing in return for help in resolving the guerrilla wars of Namibia and Rhodesia.

The shift became apparent during Secretary of State Cyrus Vance's negotiating trip to Pretoria last week. It was confirmed at the trip's end by U.S. officials, who declined to give details on what they described as a deliberate, high-level choice by the administration to use more carrot and less stick in dealing with Pretoria.

The inconclusive results Vance achieved in three days of negotiations on Namibia with South Africa's new prime minister, Pieter Botha, left unclear whether the "more normal relationship" President Carter specifically offered the South Africans will in fact develop. Carter's offer was heavily conditioned on Botha's response on Namibia and Rhodesia.

But merely by raising the prospect of 'linkage," the president has signaled a shift away from complete reliance on cooperation from key black African states in resolving the two wars on South Africa's frontiers and ultimately in persuading South Africa to diamantle its harsh system of racial segregation known as apartheid.

The shift poses risks for the hard-won gains the Carter administration has made in the black Africa, which is likely to view any such move with suspicion. The offer appears to have created strong doubts even within the administration's Africanist establishment.

At the same time, the new posture raises some intriguing questions about the foreign policy "fine tuning appears to be going on now in an administration that came to office with heavy public emphasis on its moral commitments to seek long term fundamental changes in the way the world is structured. In recent months the administration appears to be increasingly going for obtainable interim goals even if they are not guaranteed to lead to the final comprehensive targets orginally endorsed by Carter.

In the case of Africa and the Middle East. Carter has chosen to elevate the problems from the professional, diplomatic levels at which they have been handled to a personal, political level in which he essentially takes charges.

Moreover, those changes are occurring in two areas where the administration had sought particularly to distinguish its policies from those charted by Henry A. Kissinger's "step by step" approach to Middle East negotiations and by his policy of "communicating" with the white minority governments of southern Africa.

Eighteen months ago, Carter sent Vice President Mondale to Vienna to tell the South Africans bluntly that majority rule would eventually come to their land one way or another and that the United States would no longer support the "linkage" that Kissinger had suggested in his talks with them.

The confident, charged State Department and National Security Council officials who helped Mondale deliver the Vienna message denounced Kissinger's approach of offering not to press South Africa on "domestic matters" such as apartheid as long as Pretoria used its influence to resolve the problem of Namibia (also known as Southwest Africa) and Rhodesia.

In Pretoria last week, some of those same officials were along, but they appeared more subdned and less quick to criticize linkage. They knew that Vance was carrying for Botha a partly handwritten letter from Carter inviting the South African to visit Washington officially once the Namibia dispute was settled.

Moreover, the letter reportedly said that a "more normal relationship" could be established between Washington and Pretoria if South Africa used its influence constructively, in American eyes, in Namibia and Rhodesia.

At a news conference here Thursday, Vance declined to discuss what he called "the exchange of correspondence" between the two leaders. In reponse to question, however, he said that a Namibia settlement "would have a beneficial effect" in the region and "would help in terms of the atmosphere between the United States and the government of South Africa." Asked specifically if the three days of talks between the five-nation "contact group" he headed and South Africa had touched on South Africa's domestic racial situation, Vance would say only that "I had general discussions covering a whole variety of issues with the prime minister."

U.S. officials said later that nothing Vance or the other delegations said during the talks conveyed any promise to Botha that he could ever win Western support for apartheid, which the Carter administration will continue to oppose. These officials suggested that what is at stake is the form and frequency that opposition will take.

While taking the more conciliatory approach toward Botha, who has been in office only three weeks and, who is reported by South African journalists to enjoy the official's pomp enormously, the five nations also reminded him that the stick is not far from reach.

Acting at the private request of all five nations, French Foreign Minister Louis de Guiringaud told reporters in Paris just after the conference in Pretoria opened that the West would not oppose a U.N. move to impose economic sanctions this time if Botha refused to continue talks on Namibia.

In Pretoria, the personalized, flattering approach adopted by Carter to Botha paralleled in some way the president's stroking of Egypt's Anwar Sadat and Israel's Menachem Begin at Camp David. The invitation, the first to a South African prime minister since the National Party took power and installed apartheid in 1948, was reportedly Carter's idea.

The proposed movement back to some linkage with Pretoria, which implies a letting up in the harsh criticism the administration has leveled at the white government, may also parallel what some Carter advisers portray as the pragmatic movement at Camp David away from the Administration's earlier campaign for a "comprehensive" Middle East peace agreement that included a role for the Soviet Union said a guranteed "home -land" for all Palestinians.

The Camp David agreements, which are built around a separate Egyptian-Israeli peace agreement, shut out the Russians and fall-short of original administration goals in other areas.

Some of the senior staff members who have spent much of the past 18 months negotiating with the South Africans on a plan for U.N.-supervised elections to bring Namibia to indepen-became deeply concerned during the Pretoria talks last week that their foreign ministers, in dealing pragmatically, "were about to give the store away to the South Africans," according to one conference source."

In contrast to the up-beat mood of the Mondale mission to Vienna, there were clear tensions within the delegations in Pretoria.

U.S. Ambassador Donald McHenry, the normally ebullient diplomat who put together the contact group and is primarily responsible for the progress that has been made in the Namibian negotiations, was noticeably withdrawn and worried, refusing to talk to reporters and resembling Abraham being asked to put a child to sacrifice keep alive the change for better ties to Washington by agreeing to new discussions on the U.N. plan for elections, but he promised nothing else. He effectively bounced the ball back to Carter, who now awaits U.N. and black African reaction to the new pragmatism of linkage.