A secret speech distributed to youth leaders here has sharply criticized the United States, debunked the future of Sino-American relations, and revealed the ambivalence Chinese leaders feel about their growing ties with Washington.

A copy of the speech, distributed to Communist Youth League members throughout Peking and obtained from Chinese sources, describes the United States as a greedy, relentlessly imperialist country where a mother must pay to eat at her son's home and where much wealth has been exploited from Chinese labor.

The speaker, Qinghna University Vice President Zhang Guangdou, warned a meeting of Youth League members from Peking's several universities that "the American people are good . . . but the American government and the capitalists are imperialist. We don't want to entertain any illusions. In one sense, what we are doing now is tactical -- a united struggle against hegemonism" -- the Chinese code word for the Soviet Union.

Zhang, a hydroelectric expert whose university is the Chinese equivalent of MIT, appeared to indirectly refer to U.S. technology and trade now coming to China. In a remark addressed to Chinese on Taiwan, but also apparently aimed at his Peking listeners, he said: "Comrades, you should think. Conditions in the world are changing rapidly so that in the future the American people and the Japanese will change their stripes. They won't care for you after you have no more resources."

Since a wave of pro-American articles swept the Chinese official press during the U.S. visit of Vice Chairman Deng Xiaoping last year, the Peking press has tried to redress the balance by printing occasional articles criticizing American life.

But none of the articles have called into question the future of the Sino-American relations as Zhang's remarks do, nor have they been so vehement in their criticism of American society.

At the same time, Zhang supports the current official Chinese effort to "seek truth from facts" by pointing out that living standards in the United States and Taiwan are much higher than in China.

He does this in a backhanded fashion that includes some distortion. Zhang, who studied in the United States 40 years ago and returned for a two-month visit recently, said, "We saw that all Americans have cars, workers have cars, and they also have nice houses. . . . But this is only one side of the coin. The other side is that wealth in America is very unevenly distributed. Capitalists lead a life of debauchery and waste. If they have a child who marries, they might spend one or two million dollars on one banquet. Most of the workers are very nervous and worried. Money is still not ample and most of the produced wealth is still siphoned off by the capitalists."

Zhang's speech confronts the central dilemma of the recent turnabout in Chinese foreign and domestic policy: how can Communist Party leaders argue that socialism is better than capitalism as they become friendly with and receive assistance from capitalist countries? The solution, to judge from Zhang's speech, is to debunk the West in strong terms privately and cast doubt on the future of the relationship with the United States, while continuing to make friendly statements in public.

"Is socialism good or is capitalism good? Right now, this issue is very confused," Zhang said. He answered his own question by attacking the United States: "It oppresses and exploits domesticly. Abroad, it is expansionist, grabbing many colonies. Does the United States have colonies? On the surface, it doesn't appear to have any. But in reality, it is neocolonialist. It frightens you and controls you and constructs military bases. It has military bases in Spain, Western Europe, Africa and Asia. "The United States talks about democracy, freedom and human rights. What kind of human rights are these . . . At the beginning of their development, they bought many black people and brought them to America from Arica. In addition, there were many Chinese who migrated. At that time, China was decaying, and many people's lives were terrible. Therefore Americans and other foreigners seduced Chinese people into going to America . . . They were exploited worse than oxen and horses, and many died.

"The last time that I went to the United States, I saw many former classmates who had not returned to China. They had become Chinese-Americans. They are always figuring and figuring, worrying that there won't be enough money. My standard of living is low [in China] but I am not anxious.

"The United States also has great unemployment, and in the American social system there are family problems. If a son goes to his mother's home to eat, he must pay money. If the mother goes to son's house to eat, she must also give money. I'm not joking in the least. I'll give you an example. A family invited me to eat dinner. Four of them invited me, and after eating, and in front of me, they took out a calculator and calculated who owed what."