Five key African states have formally approved the latest British-American proposals for a settlement of the Rhodesia dispute, paving the way for their presentation and probable approval at the forth-coming session of the United Nations.

At the end of a two-day summit meeting in the Mozambican capital of Maputo today, the five so-called front-line countries said they regarded the proposals as a "basis for further negotiations" despite "a lot of negative points" that they said left "many questions unanswered."

This somewhat qualified endoresement was taken here as a formal acceptance of the British-American plan by the five African states directly or indirectly involved in the nationlaist guerrilla war aimed at overthrowing the white-minority Rhodesian government .

Rhodesian Prime Minister Ian Smith has condemned the Anglo-American plan as an attempt to appease Communist-backed terrorists, but his government has stopped short of rejecting it. Smith's chief objection to the plan appears to be centered on a provision calling for disbanding Rhodesia's security forces.

The African leaders' decision to back the plan was described by a top aide to Zambian President Kenneth Kaunda as a "major breakthrough" that cleared the way for further Anglo-American diplomatic moves and negotiations among the parties in the Rhodesia dispute.

Briefing Zambian journalists on the outcome of the Maputo summit, Kaunda's aide, Milimo Punabantu, was quoted in the local media as saying that the front-line leaders regarded the plan as adequate for the African nationalists in Rhodesia to proceed with negotiation with the British, Americans and their allies.

"They see the involvement of the United Nations as a further strengthening of the proposals because they are the farthest the British and their (American) friends have gone in trying to give independence to Rhodesia.

"We have never had a situation like this. The negative elements and unanswered questions will become positive and answered as negiotiations proceed," the Zambian official was quoted as telling Zambian journalists.

The African countries have never accepted the 1965 unilateral declaration of independence by the white minority in Rhodesia and do not regard the present government there as an independent one. In their view, Britian, the former colonial power, is still legally responsible for turning the Rhodesian government over to a black majority.

Attending the Maputo summit in addition to President Kaunda were Presidents Julius Nyerere of Tanzania, Sir Seretse Khama of Bostwana, Samora Machel of Mozambique and Joshua Nkomo, co-leader of the Patriotic Front, the main African nationalist group in Rhodesia. The fifth front-line leader, Agostinho Neto of Angola, and the other leading figure in the Patriotic Front, Rober Mugabe, were unable to attend because of other engagements.

The seven-point Anglo-American peace plan calls for the peaceful surrender of power by the white minority government and orderly transition to black-majority rule in the breakaway colony before the end of 1978.

It is also provides for a British resident commissioner to take over all powers during a transition period, a United Nations peace-keeping force to help maintain law and order and for free elections on the basis of one-man, one-vote for a black "independent" government.

The British and U.S. governments plan to take the proposal to the U.N. Security Council this fall for its approval and the appointment of a U.N. special representative to deal directly with the Rhodesia problem together with the British resident commissioner. They also intend to ask for the creation of a "United Nations Zimbabwe Force" that would supervise a cease-fire in the guerrilla war and help oversee the administration of Rhodesia and free elections during the interim period leading to black-majority rule. Zambabwe is the African name for Rhodesia. [TEXT OMITTED FROM SOURCE] line states, the British-American plan was doomed to failure at the United Nations. With their support now assured, it is unlikely that either China or the Soviet Union will veto the proposals inside the U.N. Security Council.

In their statement at the end of the Maputo summit, the front-line presidents suggested that they have strong reservations about some of the points in the plan. One of their chief concerns, according to Punabantu, is precisely who will be responsible for the removal of Prime Minister Smith if he refuses to surrender power peacefully.

"For the proposals to be completely meaningful, the front-line presidents want Britian and the United States to work out a method of getting Smith out of office," he was quoted as saying in The Times of Zambia.

But the African leaders seemed more anxious to point out the positive than the negative aspects of the latest British-American plan. They hailed the two Western nations' commitment to elections in Rhodesia besed on the principle of one-man, one-vote, the British agreement to run the interim government, the British request for a U.N. peace-keeping force and the agreement by the two powers that the nationalist guerrilla army, or "liberation forces," form the basis of a new national army for an independent Zimbabwe.

Prime Minister Smith has been particularly vehement in his rejection of the dissolution of the white-dominated Rhodesian security force to make way for the guerrilla forces to take over responsibility for law and order in the country, but he has also indicated his refusal to go along on most of the other key British-American proposals.

Left unclear by the front-line presidents' stand was the position of the Partiotic Front. Twelve days ago it issued a statement expressing strong disapproval of various points in the British-American plan. Among other things, it demanded that the Front's guerrilla army be involved "in all organs and functions" of the transition government.

It did say, however, that it stood ready to enter into negotiations with the British government to expedite the transfer of power to the nationalist forces.