LEVITTOWN, Pa. - Barack Obama joined Democratic presidential rival Hillary Rodham Clinton on Wednesday in calling for President Bush to boycott the opening ceremonies for the Olympic games in Beijing.

Clinton had commended British Prime Minister Gordon Brown for announcing that he will skip the August ceremonies in China's capital, and called on Obama and likely Republican presidential nominee John McCain to join her in urging Bush to do the same.

Obama did later in the day; his campaign issued a statement in which, for the first time, he urged Bush to boycott the festivities.

Activists are urging world leaders to stay away from the ceremonies to underscore concerns about China's human rights record, its handling of recent unrest in Tibet and its relationship with Sudan.

Obama said a boycott "should be firmly on the table," but that a decision should be made closer to the games.

"If the Chinese do not take steps to help stop the genocide in Darfur and to respect the dignity, security, and human rights of the Tibetan people, then the president should boycott the opening ceremonies," he said. "As I have communicated in public and to the president, it is past time for China to respect the human rights of the Tibetan people, to allow foreign journalists and diplomats access to the region, and to engage the Dalai Lama in meaningful talks about the future of Tibet."

Obama previously had said he was conflicted about U.S. participation, but that "there should be consequences" for China if it does not take steps to respect rights and freedoms in Tibet.

Clinton said Bush should use threat of a boycott to exert leverage on the Chinese government.

"I believe that the president should not attend the opening ceremonies because that it is giving a seal of approval by our United States government," she told reporters near Pittsburgh on Wednesday.

McCain spokeswoman Brooke Buchanan said he condemns "the brutal oppression" the Chinese have inflicted on Tibetans, and thinks the president should monitor the situation and "keep his options open."