US President George W Bush arrived in Beijing on Thursday to attend the opening ceremony of the Olympic Games after raising fresh concerns about China's attitude towards human rights.

The US leader, who has insisted that he does not want to politicise the Olympics, flew into the Chinese capital from Thailand, where he made a robust speech questioning China's commitment to religious and other freedoms.

Bush raised "deep concerns" about China's detention of dissidents and respect for human rights.

Speaking in Bangkok, Bush insisted that his criticism was not intended to "antagonise" China on the eve of the Games, and expressed optimism about the future of the world's most populous nation.

But he repeatedly highlighted Washington's "deep concerns over religious freedom and human rights" in China.

"The United States believes the people of China deserve the fundamental liberty that is the natural right of all human beings," Bush said.

"America stands in firm opposition to China's detention of political dissidents and human rights advocates and religious activists," he said.

"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."

"We press for openness and justice not to impose our beliefs, but to allow the Chinese people to express theirs," he said.

Critics have said that Bush should have boycotted the opening ceremony of the Games because of China's record on human rights, which has been in the international spotlight in the run-up to the August 8-24 Games.

China has meanwhile insisted that the world sporting showpiece should not be politicised, something Bush has pledged not to do.

The White House released the text of his speech ahead of time on Wednesday, two days before Bush will attend the opening ceremony of the Games.