In an effort to prevent a clash with black African nations over applying sanctions against South Africa, Western diplomats led by the United States yesterday secretly proposed a compromise that would postpone Security Council action on the sanction question for two weeks.

Reliable sources said the Western proposal, which was presented to African representatives yesterday, would suspend council debate on sanctions for two weeks while Secretary General Kurt Waldheim sounds out the South African government on its willingness to comply with a U.N. plan for the independence of Namibia (Southwest Africa).

The Africans reportedly said they would study the idea but made no immediately commitment.

The Africans reportedly said they would study the idea but made no immediate commitment.

Some observers characterized the Western proposal as a last-chance attempt to stave off confrontation and buy time to try to induce South Africa to make some gestures that will satisfy the black African states.

The plan reportedly was devised after Western diplomats decided that they and the Africans could not agree on a formula for a Security Council resolution dealing with South Council resolution dealing with South Africa's alleged defiance of the U.N. plan for pre-independence elections in Namibia.

In the absence of an agreement, sources added, the council debate, which is scheduled to resume Monday, almost certainly would result in adoption of an African-backed sanctions resolution.

That, in turn, could force the West to veto the resolution - a move that would severely strain Western relations with black Africa and reduce Wester hopes of promoting peaceful solutions to racial conflicts in southern Africa.

The controversy arose after South Africa backed out of a plan - sponsored by the United States, Britain, France, West Germany and Canada - for the United Nations to oversee Kamibia's move to independence. South Africa has ruled Namibia (formerly Southwest Africa) since 1920 under an old League of Nations mandate.

Fearing that a U.N. presence would result in pre-independence elections being won by the Southwest Africa People's Organization (SWAPO), which has been waging guerrilla war against South Africa, the Pretoria government decided to go it alone and hold elections in early December. That move has been opposed bitterly by the black Africans who see it as a South African attempt to create a puppet government.

Last month, Secretary of State Cyrus Vance and foreign ministers from the other Western powers went to Pretoria to confer with Prime Minister Pieter Botha. The result was a patchwork of deliberately ambiguous understandings that have provoked confusion and suspicion among the black Africans.

South Africa said it would proceed with its planned December elections, but it also promised to try to persuade those who are elected to cooperate in holind U.N.-organized election next spring. The Western powers, while emphasing that they would not recognize the results of the December balloting, said they would regard the South African promise as messing supervision is still on track.

Since then, the United States and its allies have argued that the best course is to wait and see whether South Africa makes good on its promise, but this call for patience has been spurned by the black Africans.

For the past week, the Africans and the Western countries, have been trying to work out a draft resolution. Informed sources said yesterday that the West has decided it cannot accept what appears to be the minimal African demand - giving South Africa two to three weeks to announce that it will comply with the U.N. plan and then applying sanctions if it fails to do so.