Critics of China say that Mr. Bush avoiding the event would be a powerful sign of international anger over China's violent response to demonstrating Buddhist monks in Tibet. British Prime Minister Gordon Brown's spokeswoman said Wednesday that Brown will not attend the opening ceremony.
Over two days, White House press secretary Dana Perino has faced questions about Mr. Bush's attendance at the opening gala for games that China hopes to use as a showcase of its rising economic and political power. She says Mr. Bush will go to the Olympics. But, pressed by reporters on whether she could say whether he will attend the opening ceremony, Perino said Wednesday, "I cannot."
She says the reason is not uncommon: "I'm not trying to signal anything by saying that; I don't have the president's schedule. It is way too far in advance for us to announce the president's schedule."
Perino said Mr. Bush "has been very clear that he believes that the right thing for him to do is to continue to press the Chinese on a range of issues, from human rights and democracy, political speech freedoms and religious tolerance, and to do that publicly and privately, before, during and after the Olympics."
Democratic U.S. Sens. Hillary Rodham Clinton, Robert Byrd and Robert Menendez sent Mr. Bush a letter Wednesday saying that the crackdown in Tibet "should be unacceptable to anyone who believes in basic human freedoms."
"We believe that your attendance at the opening ceremonies, rightly or not, would send the implicit message to the world that the United State condones the intolerance that has been demonstrated by these actions of the Chinese government," the letter said.
Barack Obama, Clinton's rival for the Democratic nomination, joined the chorus later Wednesday, calling for the president to boycott the opening ceremonies.
His campaign issued a statement in which, for the first time, he urged Mr. Bush to boycott the festivities.
Meanwhile, the U.S. House of Representatives passed a resolution criticizing China for its crackdown on protesters in Tibet and urging Beijing to hold direct talks with the Dalai Lama, the exiled Tibetan religious leader, on the future of the region.
The resolution also demanded that China release Tibetans imprisoned for participating in peaceful demonstrations and allow international monitors and journalists unfettered access to the Tibet Autonomous Region and other Tibetan areas of China. It passed 413 to 1.
A similar resolution has been introduced in the Senate. Both say the opening of further Chinese diplomatic missions in the United States should be contingent on Beijing allowing the United States to establish an office in Lhasa, Tibet's capital.
Secretary of State Condoleezza Rice told lawmakers Wednesday that the United States is looking at the possibility of a U.S. consulate in Tibet. She said the United States has urged China to allow more U.S. diplomats into the region, saying access granted by China so far was not good enough.
"The United States," she added, "has been very active in making the case to the Chinese that they are going to be better off to deal with moderate forces on Tibet like the Dalai Lama; that they should open dialogue with him."
Protesters around the world are trying to link China's poor human rights record to the staging of the Olympics. Demonstrations about Tibet have been held along the path of the Olympic torch in Paris, London and, on.
China's Foreign Ministry spokeswoman Jiang Yu condemned the House resolution, saying it "chooses to remain silent on the violence involved in beating, smashing up properties, looting and arson in Lhasa and the Dalai clique who premeditated and organized the criminal act of violence."
The Dalai Lama, who fled Tibet after a failed uprising in 1959 but remains the religious and cultural leader of many Tibetans, has said that he wants greater autonomy for the remote mountain region but is not seeking independence.
Speaking in Japan Thursday, the exiled spiritual leader said, he supports China's hosting of the Summer Olympics, but insisted nobody had the right to tell protesters demanding freedom for Tibet "to shut up."
"We are not anti-Chinese. Right from the beginning, we supported the Olympic Games," he told reporters on a stopover on a trip to Seattle, where he was to attend a conference. "I really feel very sad the government demonizes me. I am just a human, I am not a demon."
He said the demonstrators had the right to their opinions, though he called for nonviolence.
"The expression of their feelings is up to them," he said. "Nobody has the right to tell them to shut up. One of the problems in Tibet is that there is no freedom of speech."