The Rhodesian Patriotic Front guerrilla alliance has agreed to attend the British-convened peace talks scheduled for next month in London, but it has raised major objections to a settlement as envisioned by the British government.

Officials from the Front's two wings, the Zimbabwe African National Union and the Zambabwe African Peoples Union announced the decision here after two days of talks between the coleaders of the Front, Robert Mugabe and Joshua Nkomo.

In a press conference, Front officials outlined objections to the new independence plan for Zimbabwe -- Rhodesia, which was adopted by the Commonwealth heads of state in Lusaka earlier this month. The Front rejected guaranteed constitutional safeguards for the country's white minority, Britain's right to supervise new democratic elections, the step-by-step negotiation path laid down in the Lusaka accord and Britain's call for a ceasefire during the conference.

The Front's hardline position has been essentially consistent since the Geneva conference in 1976. However, since Tanzanian President Julius Nyerere, the influential head of the African group of frontline states, has evidently accepted certain of these points, including some form of constitutional safeguards for whites, the Patriotic Front may be forced to compromise during the conference.

At today's press conference, the Front made it clear it would attend the London talks even if Prime Minister Abel Muzorewa and his white predecessor, Ian Smith, were present -- so long as Britain was chairing the conference.The Front has consistently argued that it is up to Britain, the legal colonial power in Rhodesia, to oversee the transfer to true majority rule.

In a position paper signed by Mugabe and Nkomo, who left here before the press conference, the Front said that "to incorporate in a purportedly democratic constitution provisions . . . according . . . preferential treatment on no other basis than those of race and color is repugnant to the principles of democracy as we understand and cherish them."

At the insistence of Britain and in hopes of lessening fears of Zimbabwe-Rhodesia's economically and politically dominated white minority, the six-point Lusaka plan said the new constitution would include as yet undefined "appriate safeguards" for the country's racial minorities.

The Front's position paper said the new elections must be supervised by "persons or groups of persons who possess an objectivity and impartiality which is beyond question." It implied that the Front would accept supervision by either a United Nations or Organization of African Unity force.

Such a position is seen as a retreat from an earlier adamant stand by Mugabe that only a guerrilla force could supervise bew elections and that the current Zimbabwe-Rhodesian Army must be locked in its barracks.

Nyerere, for one, has been pushing the Front to accept an outside force from the United Nations, Organization of African Unity or even Britain. But the Front made it clear that it would not accept a British military presence.

In its conclusion, the position paper said the Front also "rejects . . . the proposal [by Britain] of a cease-fire" during the talks. The Front has repeatedly held that the guerrilla war will continue until an acceptable settlement is reached. On this point the Front has the full backing of Nyerere and the other frontline presidents.

The Patriotic Front's acceptance of the British invitation to the forthcoming conference was not unexpected, for the Front has consistently expressed its willingness to engage in serious negotiations under British auspices. If the Front had refused, it would have been subjected to considerable arm-twisting by Nyerere, a key architect of the Commonwealth accord.

Aides to Nyerere say that, if necessary, he was prepared to meet at length with the two guerrilla leaders to assure they accepted the British invitation. However, the fact that Mugabe and Nkomo left here without seeing the Tanzanian president indicated that they easily accepted the British invitation and met only to hammer out a common strategy for the London meeting.