Authorities in San Francisco are bracing for anti-China protests Wednesday as the western U.S. city hosts the latest leg of the Olympic torch's world relay.

San Francisco officials say hundreds of police will patrol the 10-kilometer route of the torch relay in anticipation of demonstrations by thousands of protesters. Officials say they may change the relay's route at the last minute for security reasons.

U.S. authorities hope to avoid a repeat of chaotic scenes in Paris and London in recent days in which anti-China activists disrupted the torch relay.

The Olympic torch arrived in San Francisco early Tuesday and was kept at a secret location until the start of today's relay. One runner who planned to carry the torch has dropped out.

Pro-Tibet activists and human rights groups say they encourage their supporters to protest peacefully without disrupting the relay.

San Francisco is home to one of the largest Chinese American communities in the U.S. Some Chinese American residents of the city say they are proud that Beijing will host the 2008 Olympics and say they are against the torch protests.

On Tuesday, several hundred activists marched in San Francisco to condemn China's recent crackdown on anti-government protests in Tibet. The protest culminated in a candlelight vigil with speeches by Nobel peace prize winner Desmond Tutu and U.S. actor and pro-Tibet activist, Richard Gere.

China has condemned the Olympic torch protests as "pitiable and insignificant."

The torch's next stop is the Argentinean capital, Buenos Aires, where activists are planning further protests to coincide with Friday's relay.