President George Bush in a speech in Thailand has told China that the US stands in "firm opposition" to the way the Chinese government represses its own people.
The stinging rebuke came on the eve of the opening ceremony of the Beijing Olympic Games.
But to lessen the blow, Mr Bush praised the Asian nation for its market reforms.
"We speak out for a free press, freedom of assembly, and labour rights not to antagonise China's leaders, but because trusting its people with greater freedom is the only way for China to develop its full potential,"
Mr Bush continued "And we press for openness and justice not to impose our beliefs, but to allow the Chinese people to express theirs."
"America stands in firm opposition to China's detention of political dissidents, human rights advocates, and religious activists."
The president added that he was optimistic about China's future and that young people may grow up with more freedoms. He said: "Change in China will arrive on its own terms and in keeping with its own history and its own traditions. Yet change will arrive."
President Bush was speaking the day after the first prisoner from Guantamino Bay was convicted after six years of the notorious prison camp's existence.
Allegations of 'water-boarding' torture as well suspects being flown on 'black' flights to foreign countries to be 'interegated' using methods illegal in the USA have constantly undermined America's ability to criticise other countries record on human rights.