San Francisco ? Security was tightened on the Golden Gate Bridge and elsewhere around the city Tuesday as officials prepared for massive protests of China’s crackdown in Tibet during the Olympic torch’s only North American stop on its journey to Beijing.

The Olympic flame was whisked to a secret location shortly after its predawn arrival Tuesday following widespread and chaotic demonstrations during the torch relay in London and Paris. Activists are protesting China’s human rights record, its grip on Tibet and support for Sudan despite years of bloodshed in Darfur.

The torch is scheduled to be paraded through the city today on a six-mile route that hugs San Francisco Bay. Already, one runner who planned to carry the torch dropped out because of safety concerns, officials said.

It began its 85,000-mile journey from Ancient Olympia in Greece to Beijing on March 24 and was the focus of protests from the start.

Hours after it arrived in San Francisco, protesters marched to the Chinese Consulate, calling on China to cease its heavy-handed rule of Tibet.

Meanwhile, a few miles away in Chinatown, leaders of China’s expatriate community held a news conference calling for a peaceful relay and said they were proud China was selected to host the summer games.

In Beijing, International Olympic Committee President Jacques Rogge said the body’s executive board would discuss Friday whether to end the international leg of the torch relay because of the demonstrations. He said he was “deeply saddened” by the previous protests and was concerned about the relay in San Francisco.

“We recognize the right for people to protest and express their views, but it should be nonviolent. We are very sad for all the athletes and the people who expected so much from the run and have been spoiled of their joy,” Rogge said.

Hundreds of activists carrying Tibetan flags and wearing traditional clothes gathered in United Nations Plaza, a pedestrian area near San Francisco’s City Hall, to denounce China’s policy toward Tibet and the crackdown on protesters there. They marched to the Chinese Consulate as part of a daylong Tibetan Torch Relay.