The United States and Britain called upon Rhodesian Prime Minister Ian Smith today to "surrender" power peacefully and make way for the establishment of a black-majority government elected on the basis of one-man, one-vote by the end of next year.

Presenting him with a seven-point plan for a resolution of the 12-year-old Rhodesia dispute, the two western nations asked Smith to hand the reins of government back to Britain, the former colonial ruler here, and let it arrange with the help of a United Nations peacekeeping force for a peaceful transition to black rule within six months of his removal.

To the surprise of everyone here, the Rhodesian leader did not reject the proposals immediately. Whether he would accept such a surrender of power to the British, he said, "would depend on the circumstances surrounding it."

"If everything was according to my plan, and this was just a sort of temporary phase to arrive at the ultimate objective, maybe I would have a look at it," he said, adding that the proposal is an "involved and complicated document" that would take several days of every careful study before he would give a "considered opinion."

Smith said he had been "pleasantly surprised" by some aspects of the proposals. It was thought that he was probably referring here to provisions to protect the white minority once it comes under black rule.

Smith made his comments in a press conference after completing 3 1/2 hours fof talks with British Foreign Secretary David Owens and U.S. Ambassador Andrew Young at the Rhodesian prime minister's officials residence. The meeting followed Smith's landslide victory in a snap parlimentary election yesterday that saw the crushing defeat of both his leftist and rightist - white opponents.

Later, Owens told a press conference that he believes that Smith had still not accepted the basic Anglo-American approach to a settlement. He said there are still innumerable stumbling blocks and "formidable difficulties" in the path of a negotiated settlement and that he is not "full of optimism, to put it mildly."

Young said a peaceful solution is probably out of the question since there is already a kind of "borderline chaos situation" in Rhodesia.

But he expressed hope that all the parties involved in the conflict would see the wisdom of talking to each other rather than seeing the chaos deepen and foreign powers become involved as is now happening in the Horn of Africa.

He said he had been "personally pleased" with his first meeting with Smith. "We didn't agree, of course, and yet we had, I think, a very good discussion for several hours."

The Anglo-American proposals set out in considerable detail the basis for an internationally acceptable constitutional settlement. They include the outlines for a new, combined Anglo-American-style constitution providing for an elected president and a 120-member national assembly. It would include guarantees against discrimination for blacks and against expropriation of property for whites in a bill of rights that would be enforced by an independent judiciary.

Once the settlement terms are accepted by black and white Rhodesian leaders, a cease-fire would come into effect immediately, bringing an end to the increasingly bloody guerrilla war here that is threatening to engulf all of southern Africa and involve the superpowers. In addition, the economic sanctions imposed upon this breakaway British colony by the United Nations a decade ago would be lifted.

The seven basic elements of the latest Western peace plan for Rhodesia, as spelled out at the very beginning of the 38-page document, are the following:

Surrender of power of Britain by the white-minority government and a return to "legality," meaning reversion to Rhodesia's pre-1963 colonial status.

An orderly and peaceful transition to independence in 1978.

Free and impartial elections on the basis of universal adult suffrage.

Establishment by the British government of a transitional administration with the specific task of conducting elections for an internationally recognized independent government.

A U.N. presence including a U.N. force, during that transition period.

An independence constitution providing for a democratically elected government, the abolition of discrimination, the protection of individual human rights and the independence of the judiciary.

A World Bank-managed "Zimbabwe Development Fund" of between $1 billion and $1.5 billion sponsored by Britain and the United States, which together would provide 55 per cent of the total amount. The fund's purpose would be to assure the economic stability and development of Zimbabwe, the African nationalist name for Rhodesia, during the interim period and the establishment of an elected black-majority government.

The United States would provide 40 per cent of the fund up to $520 million and Britain 15 per cent up to about $127 million.

The establishment and operation of the proposed fund, the document says, would depend upon the acceptance and implementation of the terms of the proposed plan "as a whole."

The Patriotic Front, an alliance of black nationalist factions led by Joshua Nkomo and Robert Mugabe, issued a statement rejecting the wide powers proposed for the British resident commissioner, the retention of some elements of the Rhodesian security forces during the transition to black-minority rule and the interim U.N. presence.

However, two local nationalist leaders, the Rev. Ndabaningi Sithole and Bishop Abel Muzorewa, who met with Owen and Young, expressed their pleasure in particular with its one-man, one-vote provision. But Muzorewa expressed some reservation about whether the plan would create a new national army loyal to a black-majority government.

Perhaps the most controversial aspect of the entire plan is the transition period and the nature of the security force to be established both then and after the advent of black-majority rule.

The Anglo-American plan calls for Britain to appoint a "resident commissioner" to administer the country with "full power to make laws for the peace, order and good government" and to organize and conduct general elections within six months of Smith's surrender of power.

He would also become commander in-chief of all armed forces in Rhodesia outside the U.N. peace keeping force.

Owen announced that the British government had chosen Field Marshal Lord Carver as resident commissioner designate. While he would be available for consultations with all the parties now. Owen said, he would not be formally appointed until Britain is satisfied that there would be an effective cease-fire.

At the same time, the U.N. secretary general would appoint a special representative to work with the British resident commissioner and observe that the administration of the county and elections are "fair and impartial."

The U.N. Security Council, to which the entire plan is to be submitted for endorsement, would establish a "United Nations Zimbabwe force" to supervise the cease-fire back the interim British government, and act as liason with the guerrilla forces and with the existing white-dominated Rhodesian army.

However, primary responsibility for maintaining order during the transition period would be given to the police force under the command of a person appointed by the British resident commissioner.

As for formation of a new national army, the document simply states that this will be done "in due course" after the establishment of a transitional government.

Last weekend at a meeting in Lusaka, Zambia, the five African "frontline" states called for the total dismantling of the present white-dominated Rhodesian army and its replacement by the nationalist guerrilla forces of the Patriotic Front, and the removal of Smith to assure their support of the plan.

In an apparent effort to meet this demand, Owen said in his statement that the new Zimbabwe national army would be "based on the liberation forces" but also include "acceptable elements of the Rhodesian defense forces."

Whether Smith and his government would accept a U.N. peacekeeping force is extremely uncertain, but he almost certainly will not accept letting the guerrilla army take over in the interim period. Last night he said he had not even contemplated a U.N. force in Rhodesia but refused to say whether he would reject it.