Eight African nations joined the South-West African People's Organization (SWAPO) today in accepting most elements of a U.S.-led diplomatic initiative to bring independence to the territory of Namibia, according to diplomatic sources.

South Africa, which controls Namibia, and the internal parties in the territory have not responded formally to the Western initiative, but Secretary of State Alexander M. Haig Jr. said in remarks to a civic group in Florida last Saturday that the South Africans have "basically endorsed" the Western proposals.

The affirmative joint reply to the Western proposals was formulated at a meeting earlier this week involving foreign ministers from the eight African states and representatives of SWAPO.

British diplomats in London confirmed that they had been informed by the front-line states of their general acceptance of the Western proposals but noted that the African states raised "one or two amendments to the text...which we would not want to underplay" in terms of importance, Washington Post correspondent Leonard Downie Jr. reported.

[A British official said the Western countries would prepare a second draft proposal once South Africa and the Namibian parties respond to the first. "We hope to tie up the first stage before the end of the year," the official said. In Washington, the State Department had no comment on the reports.]

A summary of the African nations' reply, which indicated approval for most of the major elements of the Western proposals, appeared here in this morning's newspapers in stories based on SWAPO sources in Lusaka.

A key Western diplomatic source confirmed that the reports were basically correct.

The Western plan is designed to assure constitutionally guaranteed rights for the white minority -- about 12 percent of the 1 million population -- after independence. The eventual constitution would require a favorable two-thirds majority. It is to this issue that the eight countries have now responded. A second phase of the plan, involving elections and a peace-keeping force to assure them, remains to be negotiated.

South Africa, which has ruled Namibia under the name South-West Africa for over 60 years, apparently raised no major objections to the proposals in discussions two weeks ago with representatives of the United States, Britain, France, West Germany and Canada during their tour of southern Africa.

Optimism among Western diplomats that South Africa will eventually accept the the plan was strengthened last night when Dirk Mudge, a white political leader in predominantly black Namibia, warned supporters they would have to face SWAPO in the next election.

Mudge, chairman of a multiracial coalition of parties called the Democratic Turnhalle Alliance, said South Africa's credibility with the United States rested on its cooperation with the independence effort.

The alliance also does not appear to have any major objections to the Western proposals. But two white right-wing parties with close ties to South Africa's ruling National Party have objected to the Western proposals, rejecting a one-man, one-vote election in a unitary state. Their objections appear to be the main reason for South Africa's reticence.

SWAPO's affirmative response, which now has the backing of Kenya, Nigeria, Zimbabwe, Tanzania, Mozambique, Zambia, Malawi and Angola, reportedly agrees with the Western proposal that a two-thirds vote of an elected assembly should adopt a constitution, which could only be altered through a "designated process." SWAPO is also said to endorse the concept of a bill of rights and an independent judiciary.

It called for a political election campaign to be run "without discrimination or fear of intimidation of any kind" and for a "balanced restructuring" of the present white-dominated police and defense forces and civil service.

There were two significant deviations from the Western plan. One was the omission of a SWAPO commitment to a three-branch government because the Africans feel the constitutional assembly should decide on the powers and organization of the various arms of the government, according to today's newspaper accounts.

The Africans also did not mention any support for "regional governments," stating only that there should be elected local governments. The regional issue may pose a major stumbling block for South Africa since it has committed itself to a system of ethnically based second-level authorities to assuage right-wing whites now wielding authority in Namibia under a regional arrangement.