The same day of his arrival in Beijing for the Olympics, U.S. President George W. Bush plans to pointedly express "deep concerns" about the state of human rights in China and urge the communist nation to allow political freedom 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. The White House released the text of the president's speech nearly 18 hours in advance, as Bush flew to Thailand from South Korea.

The speech was planned as a summary of Bush's views of U.S. strategic interests in Asia and his policies toward the crucial region during 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 over the years — 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 the sensitive matter of China's internal policies.

"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 Wednesday, 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 during Wednesday's news conference, saying, "You ought to welcome people being able to express their minds."

In Thursday's speech, the president is softening his message somewhat by saying any changes in China would have to come "on its own terms and in keeping with its own history and traditions."

"Ultimately only China can decide what course it will follow," he says.

Still, his strong message is likely to anger the leadership in Beijing.

Bush already drew the ire of Chinese officials by meeting last week at the White House with prominent Chinese exiles and dissidents.

Bush has made clear that while he is going to Beijing mostly as an Olympics fan, he would talk frankly with Chinese President Hu Jintao during their private meetings. It was also known that he would speak publicly about religious freedom after attending a Beijing church service and that the White House was trying to arrange other meetings while he is in Beijing over four days.

But his speech takes his usually gentle criticism of China up a notch.

In addition, White House press secretary Dana Perino said the U.S. would protest China's decision to deny a visa for former Olympic speed skater Joey Cheek, who was planning to travel to Beijing to urge that the Chinese government help make peace in the war-torn Darfur section of Sudan.

More than 200,000 people have been killed and 2.5 million displaced in fighting in the western Sudanese region since ethnic African tribesmen took up arms in 2003. China is considered a major player in the situation, as it controls almost of all of Sudan's oil potential and also supplies weapons to its government.

Bush kicked off the last Asia tour of his presidency in South Korea.

From there, at Lee's side, he offered poverty-wracked North Korea hope that it could someday share in its southern neighbor's economic prosperity, even while warning it first must live up to a promise to end its nuclear weapons program.

He said the reclusive Stalinist regime in Pyongyang must continue to meet the step-by-step denuclearization demands contained in a framework agreement reached in six-party talks involving both Koreas, the United States, Japan, China and Russia. The North must also improve its human rights record, Bush said.

"North Korea traps its people in misery and isolation," the president said.

North Korea expects Bush to remove it from the U.S. list of terror-sponsoring countries as soon as next weekend, as the president said he would when the North destroyed its nuclear reactor cooling tower in June.

Bush said North Korea — which has a history of unpredictability and has repeatedly used negotiations over its nuclear program to wring aid and concessions from the West — must first agree to international terms for verifying its dismantlement efforts. Even if Pyongyang is removed from the terror list, it still will be the "most sanctioned country in the world," he added.

"I don't know whether or not they're going to give up their weapons," Bush said. "I really don't know. I don't think either of us knows."

Lee called North Korea "a very difficult opponent," even though it has become increasingly dependent on foreign food aid to feed its people.

The North, which exploded a nuclear device in 2006, is believed by experts to have produced enough weapons-grade plutonium to make as many as 10 nuclear bombs, and the U.S. has accused Pyongyang of running a second weapons program based on uranium. Actual destruction of weapons — the ultimate goal of six-party talks with North Korea — is months away at the least.

Lee, a pro-American leader who took office in February, has seen his approval ratings tumble after lifting a ban on U.S. beef imports despite public fears about its safety. The public outcry prompted street protests that drew attention worldwide.

American beef was served at a luncheon that Lee and his wife hosted for Bush and his wife, Laura.