Prime Minister Pieter W. Botha has raised the possibility of South African military intervention in Zimbabwe-Rhodesia if the current peace talks in London fail and the conflict continues.

Well-informed sources emphasized today that South African military involvement was a definite possibility, especially if "confusion and civil war" were the outcome of the negotiations.

There was no reference to previous, more limited South African conditions for entering the war: if troops from Communist countries intervene on the side of the Patriotic Front querrillas fighting the Zimbabwe-Rhodesia government or to help evacuate whites.

Coming at this time, the comments appear to be aimed at giving notice to participants at the London peace talks that the South African military machine is a factor to consider in their deliberations.

Any such intervention, however, is likely to bring the same kind of international condemnation of South Africa that it received when it unsuccessfully invaded Angola in 1975 to assist one of the contending factions in that country's civil war.

The remarks may also be intended to prepare public opinion at home for a move to upgrade Pretoria's already substantial material support for Zimbabwe-Rhodesia's Prime Minister Abel Muzorewa's war effort, or to supply manpower openly to his armed forces.

The South African military establishment is known to be extremely worried about the military position of Muzorewa's forces, which, according to one source are outnumbered by the guerrillas on the ground. "I don't see how they'll win unless they set more manpower," the source said.

Monday night Prime Minister Botha told delegates of his ruling National Party in Cape Town that South Africa had an "interest in the stability immediately north of us. If confusion and chaos are created for Rhodesia by outside forces, I want to warn that the South African Parliament will have to consider what steps we are going to take because we do not want and we cannot afford confusion on our borders."

Today in Pretoria a well-informed source said, "We will stand by [Muzorewa] if we feel he has been treated unfairly and we will then face the music of that commitment."

Botha has said before that he does not believe one can reach compromises or negotiate with what he calls "Marxist forces." He regards the Patriotic Front as a Marxist force. In 1975 as minister of defense, a post he still holds, Botha sent South African troops into Angola.

The peace talks in London will soon be approaching the crucial stage at which composition of the armed forces during a transitional stage to independence will be discussed. The South African government takes the position that the present armed forces of Muzorewa should not be altered, although they could, according to one South African official, "absorb, what [guerrilla leader Robert] Mugable calls, acceptable elements' of the guerrilla forces."

Altering the present Zimbabwe-Rhodesia defense forces would mean that "[Muzorewa] would lose his last power base, the whites would leave, the bishop would be eliminated very, very soon after that, the Marxists would take over the country, there would be civil war for a couple of months, and Zimbabwe-Rhodesia would die," the well-informed source in Pretoria said today. "It would be Angola all over again," he added.