STAR APPEARANCE: Actor Richard Gere addressing a pro-Tibet rally and candlelight vigil in San Francisco on Tuesday. China's crackdown on Tibet has led to wide protests across the world. -- PHOTO: AFP

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San Francisco, with its history of activism, has girded itself against protests and demonstrations similar to, if not worse than, those at the Paris and London stops.

Local newspapers reported that three layers of police protection would surround the torch-bearers during its 9.6km run, which kicked off at 1pm local time (4am Singapore time).

A phalanx of police officers jogging on foot will surround the torch runners, who will be flanked by police officers on bicycles, who in turn will be protected by a wall of cops on Harley-Davidson motorcycles.

Police boats will also be stationed along the waterfront route as a back-up, according to the San Francisco Chronicle.

'The idea is if there is some kind of mass sit-in that blocks the road, then they can just put the torch on a boat and move around it,' a San Francisco City Hall source was quoted as saying.

San Francisco organisers have already trimmed the route of the torch relay, scrapping proposed stops at the Golden Gate Bridge and Chinatown, and officials say they may alter the course again at the last minute to throw off protesters.

Already, one runner who planned to carry the torch dropped out because of safety concerns, officials said.

The US Federal Aviation Administration also implemented a partial no-fly zone over the waterfront loop.

San Francisco was chosen to host the relay in part because of its large Chinese-American population.

Many residents spoke out on Tuesday to ask for calm and express their pride that China was chosen to host the summer games in August.

'We are begging for five hours of peace,' said Mr Sam Ng, president of the Chinese Six Companies, a prominent benevolent association.

Pro-Tibet campaigners have shadowed the flame from the moment it was lit in Greece on March 24, as demonstrators accuse China of violating human rights and protest against a crackdown in Tibet.

In San Francisco, torch-bearers are expected to encounter people demonstrating against China's grip on Tibet, as well as the country's support for the governments of Myanmar and Sudan. Nudists eager for a return to the way the Games were held in ancient Greece will also join in the demonstrations.

A protest rally on Monday saw activists hanging banners from the Golden Gate Bridge.

The flame was whisked off to a secret location shortly after its pre-dawn arrival in San Francisco on Tuesday.

Hundreds of activists carrying Tibetan flags gathered in United Nations Plaza, a pedestrian area near San Francisco's City Hall, on Tuesday to denounce China's policy towards Tibet. They then marched to the Chinese Consulate.

The day of protests culminated in an evening candlelight vigil for Tibet, with speeches by actor Richard Gere and human rights activist Archbishop Desmond Tutu, who called on US President George W. Bush and other heads of state to boycott the opening ceremonies in Beijing.

The White House yesterday left open the possibility that Mr Bush might skip the opening ceremonies.

After San Francisco, the torch - which is on its longest-ever journey, spanning 137,000km - will travel to Buenos Aires, Argentina and a dozen other countries before arriving in mainland China on May 4.

AGENCE FRANCE-PRESSE, ASSOCIATED PRESS, BLOOMBERG