Andrew Young appealed to black Africa today to believe in the Carter administration's determination to produce peaceful change in white-dominated southern Africa through economic incentives and negotiations rather than blanket sanctions and military confrontation.

But Young's lengthy invocation of the moderation used in the American civil rights movement left many of his black African listeners unconvinced, disappointed and even angry.

The U.S. ambassador to the United Nations appeared to have irritated some of his closest African associates in a speech that aides conceded was aimed mainly at a domestic American audience.

Symptomatic of the reaction at the U.N. sponsored International Conference in Support of the Peoples of Zimbabwe (Rhodesia) and Namibia (Southwest Africa) were remarks by Leslie Harriman. He is Nigeria's U.N. ambassador, a moderate in African terms and a prime mover in black African efforts to end the racial discrimination policies in South Africa.

"One could have hoped that Andrew Young would contribute to the conference and not lecture us on civil rights," Harriman told reporters. "In Atlanta, I would have listened 10 years ago with some patience, but instead I listened today with considerable irritation."

More ominously for the outcome of the week-long conference, Harriman warned, "If this is to be the [U.S.] approach there can be no common ground. We are not here to water down achievements" the United Nations has made to date in increasing economic pressure on South Africa and Rodesia.

Young's presence there - and that of Canada - had been hailed as an indication of a new Western aggressiveness in Southern Africa.

The speech appeared to have compromised Western hopes of avoiding the kind of radical resolutions the major Western powers could not endorse for fear of undermining their own diplomatic efforts with South Africa and Rhodesia.

At one point, Young drew upon the experience of the American civil rights movement in using economic boycotts against whites in the South and said that if the blacks of Rhodesia bought nothing but food and medicine for three to six months "the impact on the Smith regime (would) equal that of the armed struggle."

The suggestion later drew an angry rejoinder from Robert Mugabe, Young's fellow luncheon guest at Ambassador Harriman's residence and a leader of the Patriotic Front guerrilla movement in Rhodesia.

Mugabe said that the liberation movement began by using "strikes, sit-ins, passive resistance, but in 1972 we came to the conclusion that the only way that remained to be tried was armed struggle."

Almost half of Young's 33-minute, off-the-cuff remarks dwelt on the application of the American civil rights experience, which he claimed had culminated in Carter's election and represented "something of a revolution in the consciousness of the American people."

He credited Indian leader Mahatma Gandhi's philosphy of passive resistance and its application by the late Martin Luther King Jr. for "securing change through the use of force which did not destroy either persons or property."

He reiterated his familiar theme that the American blacks' accession to political rights" set free white Americans" and set in motion "oplitical change that now in some sense puts the South in charge of the nation."

He explained that it was "essentially black poor and sharecroppers in Mississippi" - who a decade earlier were disenfranchised - who produced the margin of victory of Carter "so that we shouted that the hands that used to pick cotton had now picked the President."

Young recalled the "silent and non-violent revolution" that inspired students to oppose the Vietnam war and awakened Mexican-Americans and American Indians and women to "forge a new coalition for change" that got Carter elected.

Carter's long association with blacks - starting with his childhood playmates - was mentioned as was praise for Vice President Walter Mondale who since his first days as a senator in 1964 had never failed to "side with the poor the oppressed, the blacks of America."

"And so I must confess that while I respect your skepticism and even your cynicism," born of many past disappointments in the African policy of the United States," there is in fact a change in America that makes me extremely hopeful about the proceedings which are going on here and the continued role of the United States in them," he said.

Young told the conference "while you must be true to your own struggle, I hope you will respect us when we are true to our own experience. If we do analysis of the racism that we find pervasive in southern Africa, we find a phenomenon with which I am very familiar and which doesn't frighten me at all for it's been part of my whole life come to me with my mother's milk."

He said he "would remind you respectfully the history of Africa has just been a history of victory through armed struggle" since most African nations achieved independence through negotiations and those which did had moved rapidly ahead economically.

"For Africa's sake I think whenever there is a possibility for negotiated settlement, the history of Africa says that is to be preferred." Only when negotiated settlements had been "totally rejected," he added, did "armed struggle become inevitable."

He pleaded "don't neglect the weapons of the economic arsenal that are at your disposal." He warned that "quite often blanket sanctions" - of the kind now under consideration by the conference - "do not produce the desired result." He argued that a "combination of pressure and incentives can be more effective."

Indirectly criticizing black African guerrillas and their allies for radical rhetoric - and so far largely unimpressive battlefield performances - Young noted that huge South African and Rhodesian military budgets and warned, "I dare say even with a mandatory arms embargo it would be very difficult to mount sufficient power to deal with problems in this area strictly through military means."