Prime Minister Margaret Thatcher hopes to avoid any commitment to further sanctions against South Africa and will accept only minimal "gestures" as a bottom line during the Commonwealth minisummit beginning here this weekend, official sources said today.

That position is likely not only to set her apart from the six other Commonwealth leaders she is to meet Sunday, but reportedly also to put Thatcher at odds with her own foreign secretary, Geoffrey Howe.

Howe returned home from Pretoria today to headlines describing his peace-making mission to South Africa as a "debacle," and his rebuff by President P.W. Botha as a "slap" in the face. As one newspaper put it in two-inch high letters, Botha told Howe to "Get Lost!"

"It looks bloody awful," said one senior government official of the abortive talks with South African officials.

Before leaving Pretoria yesterday, Howe said he could not claim "the progress I would have liked" from the trip. Other officials said privately that Howe has concluded there is nothing further to be gained from talks with the South African government.

Howe is said to believe that, given the public nature of his effort and Pretoria's unequivocal rejection, Britain has little alternative to accepting some of the sanctions the Commonwealth has proposed, and to indicating it is prepared to go even further in the near future.

The position Thatcher will carry into the Commonwealth summit will be discussed Thursday at a Cabinet meeting in which Howe is scheduled to report formally on his mission.

But an official close to Thatcher indicated she already is committed to a strategy of being "firm and reasonable" with the Commonwealth, and to arguing against immediate action. While it may be time for "gesture politics," he said, those measures to which Britain may agree will have "no practical effect" on South Africa. Among them, he listed bans on importing South African uranium, iron and steel -- all of which Britain can produce itself or get elsewhere -- and more restrictions on British investment there.

In essence, Thatcher hopes to play Britain's responsibilities within the Commonwealth off against other responsibilities to consult with the United States and the European Community before taking any significant steps. Sunday's Commonwealth meeting, the official said, is an "artificial deadline" for action.

Leaders of the 49 Commonwealth countries met last October in Nassau to discuss a program of joint action on South Africa. As a compromise between Thatcher, who considers punitive sanctions counterproductive, and the Commonwealth majority in favor of wide-ranging measures, a six-member "eminent persons group" was appointed to visit South Africa to try to promote political dialogue among all parties there. The result of that effort was to form the basis of further discussion during an August meeting in London by a seven-nation committee consisting of Britain, Zambia, Australia, the Bahamas, Canada, India and Zimbabwe.

Last month, the "eminent persons group" concluded that the South African government was unwilling to enter serious negotiations and that further discussions with Pretoria were pointless. It strongly recommended that the seven-nation committee consider adopting "further measures" to bring economic pressure on South Africa.

In the meantime, however, another international group that includes Britain -- the European Community -- met to discuss sanctions. Sharply divided on the issue, it agreed to launch a new diplomatic initiative in South Africa, headed by Howe. The results of that mission, which ended yesterday in Pretoria, are not due for EC consideration until mid-September.

Thatcher's argument to the Commonwealth will be twofold, officials indicated. First, she will repeat her opposition to comprehensive, punitive sanctions as a means to pressure Pretoria. Second, she will note that no measures can be effective unless adopted by all the world's major economies.

There is little indication that the Commonwealth is prepared to wait, however. According to Malcolm Fraser, the Austrialian ex-prime minister who served as cochairman of the eminent persons group, the "minimum effective package" of immediate sanctions includes a ban on all international air links with South Africa, an end to consular facilities there, the freezing of all overseas accounts of South African corporations and individuals, and a ban on the purchase of all bulk commodities.