For the first time in the 14-year-old guerilla war in Namibia, South Africa and its Soviet-backed insurgent foe, the Southwest Africa People's Organization (SWAPO) are to meet publicly.

The conference, to be chaired by the United Nations in Geneva beginning Jan. 7, is a climax to 3 1/2 years of effort by the Carter administration and its allies to end six decades of South African rule over the territory and thus close out the last colonial rule in Africa. It may well be a lengthy meeting.

The incoming Reagan administration will inherit this unfinished task, providing a first indication of how the political winds from Washington will blow across Africa for the next four years.

The process that led to the coming talks on the future of the last "buffer state" between the white-minority government here and black-ruled Africa also provides an instructive lesson in the limits of Western influence over Pretoria.

The talks are not the results of Western persuasion or pressure on South Africa. The West's position that economic sanctions against South Africa are not a workable option has left it with little leverage.

Two years ago, a delegation headed by then secretary of state Cyrus Vance and his British counterpart, David Owen, visited Pretoria. Despite glaring South African intransigence -- it announced the intention to hold elections in Namibia on its own terms at the time -- the Western group did not threaten sanctions.

The current initiative is the outcome of a number of concessions made to South Africa by the West over the past two months to produce some movement.

The first concession by the West was the conference itself. When the idea was first broached through well-placed leaks to the local press, South Africa immediately warmed to the idea.It then demanded the talks as a way for the United Nations to show its impartiality between SWAPO and the South African-backed internal political parties in Namibia.

Initially, Western and especially U.S. reaction, was adamantly negative. The diplomats feared such talks would derail their peace plan that the United Nations, South Africa and SWAPO all accepted by mid-1978. But the talks are now to be held.

Over that hurdle, South Africa insisted that it did not want to be a participant in the talks, preferring to take the position of a "front-line" state while the internal political parties face SWAPO directly across the table and thus achieve some international recognition.

Although SWAPO regards these internal parties as puppets of South Africa, a compromise was reached whereby the internal parties will sit at the table with only the top South African offical in the territory. A separate South African delegation is to attend as "advisers."

South Africa also demanded that the conference agenda not be restricted to discussing implementation of the peace plan, as the West and the African "front-line" states had wanted. The reason is that South Africa would prefer to have a constitution drawn up before the U.N.-supervised elections are held. Under the present plan, constitution-making is left to the winner of U.N.-supervised elections, which South African officials privately admit the socialist-inclined SWAPO will probably win.

Western officals had objected to getting into constitutional or matters, fearing this would drag out the conference or stalemate it, thus putting off indefinitely the U.N.-run cease-fire, elections and independence.

A key phrase in the U.N. document announcing next month's talks was that "other practical proposals" can be on the agenda. "We didn't want the talks confined to implementation -- otherwise, there would be no coference," said one South African official.

Finally, Western and U.N. plan so that independence could come by the end of 1981. They had hoped to get Pretoria's agreement to a definite starting date before the conference. They have not got it.

This Western track record with South Africa on Namibia suggest that the South Africans and the internal parties will be able to bring up enough procedural problems along with the constitutional issue to make the Geneva conference a lengthy round of talks or just the prelude to further discussions.

In addition, many observers believe a Reagan administration will give a sympathetic ear to the idea that, as in the case of Zimbabwe, a constitution ought to be agreed upon before elections.

South Africa appears to have come to the conclusion that Namibia must be independent. But it is hoping for some constitutional restraint and a guaranteed role for a political opposition in a neighboring country where a Soviet-backed organization is expected to take over.

All this is not to say that the Western allies' diplomatic effort on Namibia is in vain. One Western ambassador argued that they have "inched" South Africa toward a settlement and provided an alternative to the guerilla war there that has claimed more than 1,500 lives this year.

"What would be happening if we were not involved at all? he asked.