Diplomatic sources in Cape Town indicated today that South Africa had accepted the first phase of a renewed peace effort for Namibia, with qualifications, during a meeting in Bonn of five Western negotiating countries.

Though no official information on the South African qualifications was available, a Western diplomat said they "posed no problem."

However, the South-West African People's Organization (SWAPO), the main Namibian nationalist movement, and interested African "frontline states" are understood to have objections.

According to reports, this led to a rift in Bonn today, with Europeans among the five-country Western "Contact Group" urging further attempts to accommodate the black African position and the United States warning that South African resistance to compromise might undermine the whole initiative.

These are the latest developments in a protracted Western effort to dampen a regional war, with Cuban and Soviet involvement, by negotiating a transition to independence for Namibia, also called South-West Africa.

Shuttling among various countries involved in the dispute, representatives of the five Western countries--the United States, Britain, France, Canada and West Germany--have devised a two-stage negotiating approach. Phase One, to which the South Africans reportedly agreed today, involves guidelines for a constitution for an independent Namibia, followed by the election of a constituent assembly that would write the charter and adopt it.

Phase Two, viewed as far more difficult, involves actually setting up the elections, including the ticklish issue of guaranteeing impartial supervision. South Africa has objected to a United Nations role, as the General Assembly has recognized SWAPO as the representative of Namibia's people.

Under Phase One, the Contact Group has proposed safeguards to meet South African worries about whites' treatment after independence and to guard against the possibility of a SWAPO landslide giving it a free hand in crafting a constitution.

One was to protect minorities with a bill of rights, the other to have a dual electoral system, with half the seats in the constituent assembly filled by proportional representation and the other half by single-member constituencies.

The latter would make it more difficult for SWAPO to obtain the two-thirds majority in the assembly needed for constitutional changes.

On these points SWAPO and the frontline states--which include Angola, Tanzania, Zimbabwe, Mozambique, Botswana and Zambia--have dug in their heels. They perceive a concession to South Africa's own ethnically based policies and too much of a deviation from Security Council Resolution 435, in which the Western Five gained agreement on U.N.-supervised elections.

But U.S. Secretary of State Chester Crocker, aware of South Africa's mounting problems in its own backyard, is worried that it will feel unable to yield.

South Africa has controlled Namibia since it marched into the then-German colony during World War I. In 1920 the League of Nations granted it a mandate to administer the territory, but that mandate was revoked in 1946 by the United Nations. In 1971, the International Court at The Hague declared South Africa's continued occupation of the territory illegal.

U.S. fears of heightened conflict arose over the appearance in Angola of 15,000 to 20,000 Cuban troops, together with Soviet military advisers, ostensibly to strengthen Angola's defenses against South African raids.

Four years ago, the Carter administration set up the Contact Group, which developed Security Council resolution 435 through shuttle diplomacy.

At that stage, South Africa was confident that the conservative Democratic Turnhalle Allience, a coalition of ethnically based parties, would easily beat SWAPO in any free elections.

Then, with Robert Mugabe's landslide victory against similar African conservative opponents in Zimbabwe in 1979, the Pretoria government began to argue over resolution 435. At the same time, relations between Pretoria and Washington deteriorated.

With Ronald Reagan in the wings, South Africa ran the whole initiative into the sand at a conference in Geneva last January, suddenly objecting that the United Nations could not be an impartial umpire.

In mid-1981, the Reagan administration adopted a policy approach more favorable to South Africa as an ally against communist encroachment. It has sought to reassure South Africa , but some of the European members of the Five are worried that this is having a negative effect on the black African side.

Furthermore, South African general elections last year showed a strong right-wing backlash against some mildly reformist policy moves by the government. Fearing a split among the ruling white Afrikaners, the government has slowed down its reform program.