Rhodesian Prime Minister Ian Smith announced his qualifid acceptance of the principle of one-man, one-vote tonight and said he was opening talks next week in Salisbury with moderate black nationalist leaders living in Rhodesia.

Smith's surprise decision represents a bold move to undercut the latest British-American peace plan that calls for Rhodesia to "surrender" power to Britain to make way for black majority rule by the end of next year.

The move was apparently timed to take advantage of growing differences among more radical nationalist factions outside the country and the five African front-line states supporting the guerrilla war against the white minority government.

Smith now appears to have decided to sacrifice his belief in white rule forever in Rhodesia in a bid to put relatively moderate black leaders in power to retain the confidence of the 270,000 whites in a country government. There was 6.5 million blacks in the country now.

Speaking to reporters in Bulawayo in western Rhodesia, Smith said he had decided to proceed with his own negotiations "in view of the failure of the latest Anglo-American initiative."

He said there would have to be "a serious rethinking" by the British and American governments if they still intended to play a part in the search for a settlement that he, too, could accept.

Smith said black leaders in the country told him that "the only way of successfully launching the negotiations would be for the government to make a firm commitment to the principle of majority rule based on adult suffrage."

His reply, he said, was that the government was now convinced that there were other ways of maintaining standards of White culture and retaining white confidence than by means of the limited frachise now in effect.

One of the proposals of the British-American plan is the holding of elections for a president of Rhodesia on the basis of one-man, one-vote. This kind of electorate presumably would result in a black president.

Only last year, Smith said, "Never in a thousand years" would be accept this principle and certainly never during his own lifetime.

As recently as mid-October, Smith gave no hint of moving toward acceptance of universal suffrage.

Smith said talks would begin next week in Salisbury with the three Rodhesia-based nationalist factions, the United African National Council under Bishop Abel Muzorewa, the African National Council under the Rev. Ndabaningi Sithole and the Zambabwe United People Organization led by the traditional tribal leader, Chief Jeremiah Chirau.

It would probably be several weeks before a formal constitution conference got under the way, Smith said.

"It is not the kind of problem we can solve in weeks, he said, "but I would hope that within months we would be able to see result."

Smith said he was mindful of the many past failures to reach a settlement of the 12-year-old Rhodesia dispute but said, "I have gone out of my way to insure there is no repetition" of this.

"Much time has been given to contacts with the parties concerned" he added "Now that I have made this offer, I think I can safety say we can get this one off the ground."

The last round of negotiations Smith held with black nationalist leaders was in early 1976 when he met with Joshua Nkomo is talks that collapsed partly over Smith's refusal to accept the principle of one man, one vote.

Smith's announcement came after a sharp disagreement between Zambia and Tanzania over a key provision of the Anglo-American peace plan, creating a new problem for its already frustrated architects in London and Washington.

Tanzania this week came out strongly against a recent proposal by Zambian President Kenneth Kaunda that elections for Rhodesia's first black leader he postponed for several years and that the white minority government there simply hand over power to a black national unity government led by the Patriotic Front, the nationalist guerrilla front headed by Nkomo and Robert Mugabe.

The British-American plan published Sept. 1 calls for free elections within six months after Smith surrenders power to the British, the former colonial rulers in Rhodesia, and before the country's independence under black majority rule during 1978.

Tanzania indicated that it would continue to back the British-American proposals and sharply criticized Zambia for it's policy change. The five "front-line" African states, of which Zambia, Tanzania and Mozambique are most crucial to the peace iniative, formally endorsed the Western plan Sept. 23.

Since then, however, British and U.N. representatives involved in the plan's execution met stiff resistance to various provisions from both Smith and the Patriotic Front. The Rhodesian prime minister refused to attend a plane meeting Nov. 16 on Malta, stalling the British-American initiative.

His refusal to go to Malta now appears to have been motivated by his decision to attempt to bypass the Patriotic Front, which has insisted on his removal from power.

Without the united support of the front-line leaders, there was little prospects of Britain and the United States overcoming opposition from Rhodesia's black and white leaders.

However, a senior Zambian official said today that Kaunda's plan was not new and that the British and American governments should go ahead "with all other aspects" of their proposals other than arrangements for the holding of elections.

"The Americans and British should convince Smith to hand over power by a certain date to a specific group, the Patriotic Front," the official said.

He described Kaunda's proposal as only a "slight variation" on the original British-American plan that is aimed at preventing an Angolan-style civil war among contending black factions in Rhodesia.

At least five black leaders are contending for the leadership of independent Zimbabwe, the nationalist name for Rhodesia.