The three presidential candidates have joined the widespread calls to improve the human rights situation in China as protests over the country’s crackdown in Tibet continue to dog the Olympic flame on its international journey.

Sens. Barack Obama and John McCain both advocate a tougher approach toward the Chinese government, while Sen. Hillary Clinton became the first of the three candidates to suggest President Bush skip the Olympic opening ceremonies.

“I believe President Bush should not plan on attending the opening ceremonies in Beijing, absent major changes by the Chinese government,” she said.

Fifteen U.S. House members earlier this month asked the president not to attend the Olympics at all, while House Speaker Nancy Pelosi has separately called for George W. Bush to consider an opening ceremony boycott.

Barack Obama, Hillary Clinton’s rival in the contentious race for the Democratic presidential nomination, has said he is torn in his views on the issue.

“I’m of two minds about this,” the Illinois senator told CBS News in an interview. “On the one hand, I think that what’s happened in Tibet; [and] China’s support of the Sudanese government in Darfur, is a real problem.”

Yet Barack Obama added: “But I’m hesitant to make the Olympics a site of political protest because I think it’s partly about bringing the world together.”

Monday, he said in a statement: “As I’ve said repeatedly, the Chinese government must take immediate steps to respect the dignity, security, human rights and religious freedom of the Tibetan people, to provide foreign press and diplomats with access to the region, and to finally work with the Dalai Lama toward meaningful autonomy for Tibet. If they do not, there should be consequences.”

Last month, John McCain said that dealing with a rising China “will be a central challenge” for the next president, but the Republican nominee said he does not think the United States and China are “destined to be adversaries.”

“China could bolster its claim that it is peacefully rising by being more transparent about its significant military buildup, by working with the world to isolate pariah states such as Burma, Sudan and Zimbabwe, and by ceasing its efforts to establish regional forums and economic arrangements designed to exclude America from Asia,” John McCain said.

“Until China moves toward political liberalization, our relationship will be based on periodically shared interests rather than the bedrock of shared values.”

U.S. and other Western leaders have called on China to provide civil rights and freedoms to those in Tibet and to enter peaceful discussions.

Chinese authorities have, in turn, continually accused the exiled leader (the Dalai Lama) of instigating violence in Tibet - an allegation he rejects.

The International Olympic Committee has spoken strongly against any boycott of the Games, though its position on the opening ceremony is less clear.

The Olympic flame, traveling across five continents, has been met with many protests regarding China’s abominable human rights record.

The Olympic flame arrived in San Francisco, Calif, Tuesday - the only U.S. stop for the flame, wrapping up the first week of a 23-city international tour.

The flame will then return to China in May.