Countering reports of a split between the two major groups in Zimbabwe's Patriotic Front, an official in the Front said yesterday the black nationalists will remain united when they come to power within three to four months.

Josiah Chinamano, vice-president of the Zimbabwe African People's Union (ZAPU), said in an interview yesterday that Robert Mugabe, leader of the Zimbabwe African Nationalist Union (ZANU), assured him three months ago that he is committed to the unified Patriotic Front.

The New York Times reported last month that Mugabe said ZANU did not intend to share power once it rules the country. He is also alleged to have said that the ZANU forces had done most of the fighting and therefore was the major force in the Front.

"I find it difficult to believe that Mugabe said the things he's reported to have said.... ZANU has apparently issued a denial and of course I side with ZANU's denial," Chinamano said.

Crediting the Carter administration with "doing its best" to bring about a peaceful settlement in Zimbabwe (Rhodesia), Chinamano--whose trip to the U.S. is sponsored by the Council on Foreign Relations--charged the U.S. with failing to convince Prime Minister Ian Smith of the "realities of the situation."

Lost Horse

"Smith is losing and we are saying to the Americans 'don't make the mistake of supporting the losing horse,'" he said, adding that if the U.S. will not provide the Front with arms it should offer humanitarian assistance.

Chinamano questioned the recent proposal by Sen. George M. McGovern (D-S.D.) and Sen. S. I. Hayakawa (R-Calif.) to send a Congressional delegation to monitor the April 20 elections in Zim- babwe. The Patriotic Front has comdemned the upcoming elections.

Calling the McGovern-Hayakawa alliance a "peculiar marriage of convenience." Chinamano said there can be no free election in Zimbabwe with 90 per cent of the country under martial law. "What are they going to monitor?" he asked.

Chinamano charged the Salisbury government (the four-man executive council consisting of Smith, Bishop Abel Muzorewa, Rev. Ndabaningi Sithole and Chief Jeremiah Chirau) with using private armies in addition to the regular army to brutalize the Zimbabwe people.

He said the government's armies will force people into the voting booths in April. Chinamano predicted the election will lead to a government ruled by the black Muzorewa and Sithole, which will fall to the liberation forces in three to four months.

Asked what percentage of the country the Front controls, Chinamano said, "The area in which there is martial law. Ninety per cent." The people in the country accept the idea of the Front, he added.

Chinamano, who is the right-hand man of ZAPU's president, Joshua Nkomo, said yesterday the country needs complete decolonization, followed by a cease-fire and a meeting between all parties. He said the Front would submit to an internationally supervised election but not "by Smith's friend Hayakawa and (Sen. Jesse) Helms (R-S.C.)."

Chinamano said Smith's overture to Nkomo last year taught the Front that they will negotiate only as a united front and will not allow Smith to divide them. Smith's meeting with Nkomo in Zambia last year sparked rumors of a split between Nkomo's ZAPU and Mugabe's ZANU forces.

Chinamano said the failure of the U.S. to supply the Front with arms has forced the Front to rely exclusively on the Soviet Union's and other socialist countries' assistance. But he added that once in power, the Front intends to be non-aligned and friendly to both the Soviet Union and the U.S