Clinton, in a statement, cited violent clashes in Tibet and the lack of pressure by China on Sudan to stop "the genocide in Darfur."

"At this time, and in light of recent events, I believe President Bush should not plan on attending the opening ceremonies in Beijing, absent major changes by the Chinese government," the New York senator said.

Bush plans to attend the Summer Olympics ceremonies in Beijing in August and so far has resisted pressure to change his plans in response to a violent crackdown against protesters in Tibet by Chinese authorities.

China has also been accused of refusing to use its influence on the Sudanese government to get it to stop what the United States calls a genocide in the Darfur region.

Clinton has gone a step further than U.S. House of Representatives Speaker Nancy Pelosi of California who last week urged Bush to keep the option of boycotting the ceremonies on the table.

"I encourage the Chinese to take advantage of this moment as an opportunity to live up to universal human aspirations of respect for human rights and unity, ideals that the Olympic games have come to represent," Clinton said.

Clinton's Democratic presidential rival, Barack Obama, said he too was disturbed by events in Tibet and had communicated his concerns to Bush. But the Illinois senator stopped short of calling for the president to skip the opening ceremonies in Beijing.

"The Chinese government must take immediate steps to respect the dignity, security, human rights and religious freedom of the Tibetan people," Obama said. "If they do not, there should be consequences."

Speaking before Clinton's statement was released, White House spokesman Tony Fratto said that, "We have a great deal of concern about human rights in China."

"We have never been afraid to express those views," he said.

He said the Bush administration expects American athletes to participate in the Olympics.