Rhodesian black-nationalist leader Joshua Nkomo today angrily denounced moves by the U.S. Senate and some British members of Parliament to send observers to what he termed the "nonelections" for limited black majority rule in Rhodesia scheduled for mid April.

He indirectly conceded, however, that his guerrillas were powerless to stop the elections and that Salisbury might well succeed in carrying off the voting if not in actually governing.

Nkomo demanded that the American and British governments make clear now their attitude toward the forthcoming elections and warned that if they recognized the results they would end as they did in Iran, voicing support for a government even as it was being overthrown.

"If the British and Americans are supporting the nonelections, they must come out in the open and say so," he told a press conference here. "They must stop the absurdity of hiding behind their transparent fingers."

He accused the two Western governments of adopting the same "ambivalent stance" toward the elections as they had earlier toward their own proposals for a settlement of the 14-year-old Rhodesian dispute.They finally dropped these proposals as a basis for negotiations at the insistence of Salisbury's interim biracial government.

It the United States does not condemn the elections, Nkomo said, "we shall take it that they have accepted that they are collaborators" of the Rohdesian government and "conspiring against our people.

"We are going to free ourselves anyway, that they must know," he added.

Nkomo is coleader of the Patriotic Front alliance, which has refused to take part in the elections and vowed to topple by force the new black-led government in Rhodesia. The Front has perhaps 40,000 guerrillas fighting inside Rhodesia or under training in neighboring black states.

Nkomo charged that it was "hypocritical" of the two Western governments to say they were sending no official observers to Rhodesia and at the same time offering "all facilities" to their legislators wishing to attend the elections.

"If members of Parliament and Congress, given facilities by their governments to travel to Rhodesia, are not official observers, then one wonders who is. They cannot, by any stretch of the imagination or generosity, be described as private observers," he said.

Nkomo's strong criticism of British and American legislators to go to Rhodesia as observers came amid the first indications that he now expects the Rhodesian government will succeed in holding a semblance of genuine elections. At the same time, Rhodesian Prime Minister Ian Smith was predicting "framatic movements" in southern Africa in favor of the new black-led government.

His remarks also coincided with the fall of the British Labor Party government, which may well be replaced by a Conservative one far more disposed to lift economic sanctions on Rhodesia, particularly if the Rhodesian elections are an apparent success.

Smith has long sought to have Western nations lift United Nations-imposed sanctions as a step toward recognition of his government. Observing the elections is seen as a move in that direction.

In a prepared statement, Nkomo at first asserted that "no elections, let alone free, fair and democratic elections, can be held in a raging war, in a state of emergency on top of which has been added martial law."

In answering questions later, however, he drew an analogy to the recent elections in Namibia (Southwest Africa) where more than 80 percent of the black population voted, according to official South African figures.

"In elections where there are no voter rolls, anybody conducting those elections will by the end of the day stand on the steps of city hall and make any announcement out of the figures he has computed himself," he said.

"You cannot stop them from reading numbers. They are going to read their numbers but the real elections will not take place."

Nkomo charged that Rhodesian Army auxiliaries loyal to Bishop Abel Muzorewa and the Rev. Ndabaningi Sithole, the Rhodesian government's most prominent black leaders, were already coercing Africans into voting at the elections.

Nkomo seemed to be predicting that under such duress the black population was bound to turn out in large numbers and that this would fool reporters and international observers into believing the elections were a success.

"A sea of black faces," he remarked, mimicking a British radio report on the Namibian elections. "It is going to happen and we know it is going to happen."

Nkomo said the new Rhodesian constitution providing for the April elections was "a fraud and totally unacceptable" because it did not provide for a real transfer of power from the white minority of 250,000 to the black majority of 6.7 million.

He complained that the whites, representing only 3 percent of the total population, were given 28 of the 100 seats in the new Parliament-an overrepresentation nine times their number.

[U.N. Ambassador Andrew Young criticized the Senate vote, saying that the elections in Rhodesia "are not free and fair" since they were "set up and controlled by a tiny white minority in power." He urged the House not to go along with the Senate and suggested that Congress conduct an investigation after the voting if it wants to.]