Rhodesian guerrilla leader Robert Mugabe said here yesterday that he no longer regards the Carter administration as "impartial" in the Rhodesian dispute and warned that its involvement in the search for a negotiated settlement might now be unacceptable.

Mugabe called the latest Anglo-American proposals for a Rhodesian settlement "nonsensical" and held out little hope for the U.S. and British efforts to bring together all the parties in the bitter dispute at one conference.

Calling Rhodesian Prime Minister Ian Smith's visit to the United States "tacit recognition" of his white-dominated government and a "somersault" in the administration's policy, Mugabe said his party was reviewing its whole position toward the American role and soon would issue a formal statement.

"We don't have to negotiate with the United States," he said in an interview. "The only colonial power is Britain.

"If the United States is now actually subverting us and suddenly introducting the issue of legal recognition of the internal [Rhodesian] regime, then in our opinion it has exceeded the limits of the jurisdiction we have allowed it," he said.

The United States is "no longer unbiased . . . no longer impartial," he added.

In any case, the bespectacled guerrilla leader held out little hope for the success of British and American efforts to convoke a conference of the Rhodesian biracial traditional government which the two externally based coleaders of the black nationalist Patriotic Front, Magabe himself and Joshua Nkomo.

"I don't see the possibility of an all-party conference yielding any settlement," he said. "To hold a meeting is one thing. To agree is another. So the war has got to continue."

Mugabe said new British-American proposals for a settlement eliminating the need for a elections had come as "a real surprise" to him "because all along the British had been accusing us of wanting to circumvent elections and impose a dictatorial government."

He said his party, the Zimbabwe African National Union (Zanu), was sticking to its position that elections should be held for a new black majority government before Britain recognized the country's formal independence.

Elections for a black majority government initially were regarded as the key British precondition for recognition of Rhodesian independence. But Britain and the United States have now submitted new proposals that would grant Western recognition of an interim transitional government.

There has been no reaction yet from Mugabe's co-leader of the guerrilla Patriotic Front, Nkomo. Western observers here have suggested that the new proposal may be an attempt to split Mugabe and Nkomo so that the later might reach an agreement with Smith.

Britain, the former colonial power, has never accepted the unilateral declaration of independence by the whites of Rhodesia 13 years ago. Last fall, Britain and the United States published a plan for a peaceful transition to black majority rule and the two Western powers have been trying ever since to arrange a peace conference including all parties.

Mugabe said that when British envoy John Graham and U.S. Ambassasdor Stephen Low first presented the latest Western peace plan to him here in early September "we just looked at it and laughed."

"There they were running away from the democratic process - their own elections," he said. "We have now to chase them and try to whip them into line . . . Tha's a very strange phenomenon."

Mugabe is generally regarded in the West as the most radical of Rhodesia's black nationalist leaders because his party was openly adopted a Marxist-Leninist line and had been primarily responsible for the escalation of the guerrilla war over the past six years.

Mugabe said he viewed the new British-American peace plan as aimed at merging the present transitional government with the Patriotic Front in a new governing coalition where he and Nkomo would be in a clear minority. There are now three black leaders serving on a ruling Executive Council with Prime Minister Smith.

one of the black leaders, the Rev. Ndabaningi Sithole, is presently visiting the United States with Smith.

"I cannot see ZANU being in the majority," said Mugabe. "We have definite policies we would like to safeguard. We regard ourselves as the most revolutionary organization in the country. What we have set in motion, we would like to preserve. But the others would like to destroy it," he said, referring to the black and white leaders in the transitional government headed by Smith.

Relaxed, smiling and appearing extremely confident, Mugabe predicted that the Patriotic Front could win the war in Rhodesia within two years.

"Given the necessary quantity and quality of arms, I don't give Smith another two years unless some very major support comes his way by way of open military assistance from the Western powers," he said. But even Western troops and arms "cannot save him," he added.

He said ZANU now had established "fully liberated zones" inside Rhodesia with around 750,000 of the country's 6.7 million blacks living in them. Rhodesian planes might overfly these areas, but ground troops no longer came into them, he said.

The Patriotic Front is in a position to win either way, he suggested, whether the war is fought to the finish or elections are held under British or U.N. auspices. But he ruled out any elections before independence if the Front wins on the battlefield.

"We would like to see that stage (elections) fulfilled before independence is granted," he said. "Of course, that is not to say that if we win through the barrel of the gun we will have elections before independence. We will establish ourselves in power and then work for the elections thereafter."