SAN FRANCISCO — Thousands of protesters are expected to jeer the Olympic torch on its visit here today, but local officials, Chinese diplomats, and Olympic organizers are intent on heading off the chaos that disrupted torch relays in London and Paris this week.

The announced torch route along San Francisco’s famous waterfront may be altered at the last minute to counter any attempt to block the torch, San Francisco’s mayor, Gavin Newsom, announced.

China, which is hosting the 2008 summer games in August, was eager to have the torch come to San Francisco because of its large concentration of Chinese-Americans. However, Olympic officials may not have given adequate consideration to the city’s reputation as a hotbed for liberal protest. Activists planning to demonstrate along the torch route run the gamut from Tibetan groups to Falun Gong devotees to critics of China’s failure to press for an end to the genocide in Sudan’s Darfur region.

In what may be a preview of today’s demonstrations, almost 1,000 pro-Tibet activists marched in a chilly wind yesterday to the Chinese Consulate from San Francisco’s City Hall.

“The protests taking place all over the world send a clear message to the Chinese. They show that the international community does not accept what China is doing and they cannot fool the international community with their propaganda torch,” the president of the San Francisco Tibetan Youth Congress, Tenzin Dasang, told the crowd.

Cries of “China lies, Tibetans die!” and “Tibet belongs to Tibetans!” went up from the marchers, who were led by several Buddhist monks bearing a portrait of Tibet’s spiritual leader, the Dalai Lama.

A sea of Tibetan flags filled the street in front of the shuttered consulate. The crowd roared as an airplane passed overhead with a banner reading, “Stop Cultural Genocide in Tibet.”

While protest leaders shouted in indignation at anyone inside the Chinese mission, police and interlocked metal barriers headed off any violence. As attention to the Olympic torch visit built last month, someone threw an incendiary device at the consulate’s door. The incident is unsolved.

A New York-based activist, Lhadon Tethong of Students for a Free Tibet, told the group that the recent uprising against Beijing’s rule was amazing in light of the nonconfrontational attitude most in the West take to the Communist regime. “Nobody stands up to China. None of our governments stand up to China. None of our corporations stand up to China,” she said. “Six million Tibetans stood up to China.”

Still, Ms. Tethong said her community has been touched by the recent outpouring of support. “I think the world is on our side and I think the Chinese realize that,” she said. Those seeking to use the Olympics to shame China over its conduct in Tibet got a boost yesterday from a prominent religious leader and Nobel Peace Prize winner, Archbishop Desmond Tutu. Speaking to a foreign policy forum in San Francisco, he joined the call for world leaders to boycott the Beijing Olympics.

“None of the heads of state ought to go,” Archbishop Tutu told members of the World Affairs Council of Northern California.

The archbishop made the comment after making clear that he does not think countries should keep their teams at home. “I’m not going to say we should boycott the Olympic Games because you think of all the athletes who have spent so much time preparing for this individual moment in time.”

The Anglican archbishop, who played a key role in dismantling apartheid in South Africa, said Beijing’s recent crackdown on Tibet was severe and unwarranted. The Chinese government has said 19 people died in recent unrest, but independent confirmation of the toll is all but impossible. Tibetan activists insist the number is much higher.

“At this moment, we’re chatting away, and at this moment, people are dying. People are being roughed up — totally unnecessary,” Archbishop Tutu said. “You feel impotent. You feel — is it right even to be discussing it so rationally? … You know people are undergoing the most awful experiences.”

The archbishop urged China to resume its dialogue with the Dalai Lama. “I just hope China would get to realize that her best interests are really served listening to the Dalai Lama,” Archbishop Tutu said. “He has said we don’t want to separate from China. … You couldn’t be more conciliatory, I think, than he has been.”

A former Olympic rower who joined the Tibetan protest, Charles Altekruse, said it is possible to protest China’s policies while respecting the athletes. “Once the games start they should not be disrupted. Too many people have worked too hard to fulfill their dreams,” he said. “Everything else that happens before and after, I think, is fair game … The Chinese did not want to sponsor the Olympics because they believe in sports or because they necessarily believed in the ideals of the Olympic Games. They want it for political theater and we ought to have the right to engage in our own political theater,” he said. “If we were to gather today in Tiananmen Square in China we would have all been arrested. I think there’s a great irony in that,” he said.

The torch itself was whisked into the city from the airport under cover of darkness early yesterday. In light of the protests in Paris and London, San Francisco officials are shifting from public relations efforts to a last-ditch attempt to head off a violent fiasco. A spokesman for the torch relay, David Perry, sent an e-mail to journalists saying no further interviews would be arranged with torchbearers or local organizers of the relay. “Our entire team is focused on tactical logistics,” Mr. Perry said.