Andrew Young, the American ambassador to the United Nations, won over yet another outspoken African critic today and warned that the United States would not be sucked into helping the white-minority Rhodesian regime "under any circumstances."

The new convert was William Eteki, the previously hostile leader of the Organization of African Unity, which groups all independent black African and Arab states on the continent.

Young also conferred with representatives of Marxist Angola and Polisario, the Algerian-backed movement fighting Mauretania and Morocco for control of the former Spanish Sahara.

After a morning session with Eteki, Young said, "I've given him explanations of U.S. policy and maybe we cleared up some misunderstandings."

Eteki said he was "pleased by the new U.S. policy and the new U.S. leadership," but added that Washington "can do more by putting pressure on the racist regimes" in Rhodesia and South Africa.

Young told reporters that Rhodesian military threats against Zambia and incursions against Botswana, Rhodesia's neighbors to the north and south, respectively, constitute a "deliberate attempt to try to escalate the conflict" by Rhodesian Prime Minister Ian Smith to win support.

"Smith is trying to get the liberation movement to bring in Cuban troops and thus internationalize the conflict," Young said, and added. "We will not be brawn into a conflict on his behalf under any circumstances."

Young said Smith's recent behavior made Western efforts to find a negotiated solution for Rhodesia "much more difficult."

Young was pressed about American willingness to support the tough economic sanctions against Rhodesia and South Africa that are under consideration here at the week-long United Nations - sponsored conference in support of the peoples of Rhodesia and Namibia (South) west Africa).

He said he is "not sure" that the United States would support many of the sanctions proposed by the more radical black African nations.Asked specifically if the United States would agree to severing air, shipping and other links with South Africa, Young said that would be "almost impossible for us to do."

Perhaps because of the major Western interest and presence here, many speakers displayed a new moderation in their formal declarations.

The Cuban delegate, for example, said, "We do not oppose a peaceful solution [in southern African], which could save the lives of many patriots and maybe of innocents among the white minorities themselves," a departure from past calls for armed struggle as the only solution.