BANGKOK, Thailand — The same day of his arrival in Beijing for the Olympics, President Bush plans to pointedly express "deep concerns" about the state of human rights in China and urge the communist nation to allow political freedoms for its citizens.

"America stands in firm opposition to China's detention of political dissidents, human rights advocates and religious activists," Bush is to say in the marquee speech of his three-nation Asia trip. "We speak out for a free press, freedom of assembly and labor rights — not to antagonize China's leaders, but because trusting its people with greater freedom is the only way for China to develop its full potential."

Bush is to deliver the address in a Bangkok, Thailand, convention center on Thursday morning to a crowd of foreign diplomats, Thai government leaders and business officials, before flying to China later that day.

Bush arrived in Bangkok today, and then traveled immediately to a meeting with Thai Prime Minister Samak Sundaravej.

The White House released the text of the president's speech earlier today, nearly 18 hours in advance, as Bush traveled to Thailand from South Korea.

The speech was planned as a summary of what Bush says is the "stronger engagement" with strategically crucial Asia that has marked his presidency. But his remarks on China, among his most directly critical ever in public, stand out.

He says he has built a relationship with China's leaders — through opposing independence for Taiwan, cooperating in negotiations over North Korea's nuclear program and sharing economic interests, for example — that has allowed him to be "honest and direct" on sensitive internal matters.

"I have spoken clearly, candidly and consistently with China's leaders about our deep concerns over religious freedom and human rights," Bush says in the prepared text.

Earlier today, during a news conference in Seoul with South Korean President Lee Myung-bak, Bush said China's pre-Olympics crackdown on dissent has been "a mistake."

The communist country considers the Olympics a source of huge national pride and is pulling out all stops to ensure no embarrassments. It has rounded up dissidents, detaining some. Journalists covering the games have objected to restrictions on Internet sites, worried about possible censorship.

Bush objected, saying, "You ought to welcome people being able to express their minds."