Britain and the United States reportedly have dropped their insistence on elections as a precondition of Western recognition of an interim biracial government in Rhodesia.

The new version of the Anglo-American peace plan for Rhodesia, known simply as Option B, also is said to drop the requirement that terms of Rhodesia's legal independence be agreed on at the all-parties conference the two Western powers are trying to convene.

The new proposals furthermore reportedly call for the end of British economic sanctions as soon as the conference adopts a "transitional constitution" and agrees on a new governing council including nationalist guerrilla leaders, who probably would dominate.

In dropping their demand for immediate elections in Rhodesia, the British and American governments appear to have accepted an idea put forward by Zambian President Kenneth Kaunda last fail but quickly dropped in the face of strong opposition from London. Washington and the capitals of key black African states that support the guerrillas fighting the government of Prime Minister Ian Smith.

The new Anglo-American approach seems to reflect a belief that movement is urgent if a black majority government capable of gaining international recognition is to be installed by the end of this year.

Whether the Carter administration will press the new plan on Smith during his current visit to the United States was not known here. Smith, who arrived in the United States yesterday, is expected to appeal for American support of the struggling transitional government and to continue to resist Anglo-American pressure to force it to attend a conference with its guerrilla foes.

Sources within the Patriotic Front, the guerrilla alliance, disclosed details of the revised Anglo-American plan here Friday.The new proposals reportedly were presented to all the parties to the dispute last month.

Consideration of the new proposals appears to be at too early a stage to indicate that they are acceptable to the Patriotic Front, the white-dominated Rhodesian transitional government (See AFRICA, A21, Col. 1) (AFRICA, From A1) or the five black-ruled "front-line" states that border Rhodesia and support the guerrillas.

Western observer here were skeptical that either Patriotic Front contender Robert Mugabe or the two [WORD ILLEGIBLE] black leaders in the Rhodesian government, Bishop Abel Muzorewa and the Rev. Ndabaningi Sithole, would support them. They said they believed the plan may have been deposed to tempt the other Patriotic Front leader. Joshua Nkomo, and Smith to reach an agreement.

Meanwhile, Mozambican President Samora Machel and Tanzanian leader Stulius Nyerere flew together to the Zambian capital of Lusaka yesterdy, reportedly to discuss the new Anglo-American proposal with Zambian President Kenneth Kaunda.

The three front-line presidents are also expected to review the implications of Zambia's decision to reopen its border with Rhodesia in order to have access to South African ports.

Neither Machel nor Nyerere is thought to be pleased by lossening of the Zambian economic blockade of Rhodesia at a time of growing confrontation between Patriotic Front guerrillas and the Rhodesian transitional government.

The main points of the new 12-point plan as explained by Patriotic Front sources here are:

An all-parties conference would agree on a "transitional constitution" and on a new governing body, combining the present four-member ruling Executive Council in Rhodesia and the Patriotic Front's two co-leaders, which would be rule until elections are held.

After agreement on a transitional constitution, the British Parliament would approve lifting of the economic sanctions that were imposed by the United Nations at Britain's request shortly after Rhodesia's white minority declared the colony independent of Britain in November 1965.

The new interim Rhodesian government would then hold a general referendum on the transitional constitution.

If the referedum is approved, the British Parliament would formally grant independence to Rhodesia with out waiting for election of a new black leadership.

A British resident commissioner would serve during the transitional period, and would have executive and legislative powers over defense, law and order, and "certain reserve powers over external relations." It appears that the commissioner would not be chosen until after the formal grant of independence, and would be a joint appointee of Britain and the new governing council.

(It appears that the British commissioner would not be the all-powerful figure he was meant to be under the earlier British-American proposals. Both Prime Minister Smith and the Patriotic Front leaders had objected to his sweeping powers.)

There would be a "United Nations presence" but not necessarily a U.N. peacekeeping force such as was proposed under the earlier plan.

The new proposals are unclear on the knotty issue of the composition of the armed forces during the transition period, and the dismantling of the present white led Rhodesian Army as demanded by the Patriotic Front.

Some reports circulating here and in Lusaka say, however, that the British and American governments have been sounding out all parties on the idea of leaving both the guerrilla forces and the Rhodesian Army intact until after the transition is completed and a new black majority government is in power.