The Olympic torch arrived for its only North American stop on Tuesday amid reports that the International Olympic Committee will consider cancelling the international leg of the relay in light of anti-China protests.
News of a possible review of the relay comes in the wake of violent protests by pro-Tibet activists who have interrupted the Olympic torch runs in London and Paris.
The Associated Press quoted International Olympic Committee president Jacques Rogge on Tuesday as saying he was "deeply saddened" by the demonstrations and that the IOC's executive board would discuss abandoning the international leg in a meeting Friday.
Gunilla Lindberg, a vice-president of the IOC, also told reporters that "I think we need to have a full review."
Emmanuelle Moreau, an IOC spokeswoman, told CBC News that it was "likely that the subject of the torch relay be discussed at some stage during the upcoming executive board meeting.
"This would be natural, given the recent events," Moreau said.
Torch run 'hijacked,' says Pound
IOC committee member Dick Pound told CBC News that he wasn't sure cancelling the international leg of the relay was a good idea, but said the run is allowing "a peaceful agenda to be hijacked by somebody with a completely different agenda."
"Nobody likes what goes on in Tibet. We'd like to see a solution for it, but to build your entire response to the China-Tibet problem on the back of a team of synchronized swimmers and other athletes at the Games I think is wrong and counterproductive."
He added he has never supported an international torch relay because of the logistics and risks involved.
The 137,000 kilometre international trek, which stops in 20 countries, is the longest Olympic torch run ever staged. But activists opposed to China's policies toward Tibet and Sudan have used the event to bring attention to their causes.
Canada is not on the torch relay route.
Security beefed up as flame arrives San Francisco
The torch arrived under heavy security in San Francisco at 4 a.m. on Tuesday, a day ahead of the full relay along the city's waterfront. The flame was immediately put into a vehicle and whisked away to a secret location.
"We treated it like a head of state visit," airport spokesman Mike McCarron said.
But fears of protests were already circulating. One runner who was scheduled to carry the flame has dropped out because of safety concerns, David Perry of the San Francisco Olympic Torch Relay Committee confirmed Tuesday.
He would not identify the runner.
Protests against the Chinese government have already sprung up in the California city, as three pro-Tibet activists climbed the suspension cables of the Golden Gate Bridge on Monday to protest arrival of the torch relay.
The protesters unfurled two giant banners reading "One World, One Dream" and "Free Tibet '08" — a play on the official slogan of the Beijing Games. One of the climbers also displayed a Tibetan flag.
The climbers, and four people who helped them, were arrested and charged with trespassing, conspiracy and causing a nuisance. One of the four helpers was a Canadian student who attends the University of British Columbia.
The last segment of the torch's run through Paris was cancelled Monday after thousands of anti-China protesters repeatedly prompted officials to halt the procession, extinguish the flame and put the torch aboard a bus.
French President Nicolas Sarkozy told reporters Tuesday that the Paris disruption was sad spectacle, but that protests are normal in a democratic country.
Despite intense security, the relay had to be suspended at least five times in Paris as demonstrators threatened the torch. A vehicle carried the Olympic flame for the last part of the route, but a runner was allowed to carry the torch for the final five metres into a sports stadium in the south of Paris.
On Sunday, police repeatedly scuffled with protesters in London, including one who tried to grab the torch, while another tried to snuff out the flame with what appeared to be a fire extinguisher.
After San Francisco, the torch is scheduled to travel to Buenos Aires and then to a dozen other countries. It is scheduled to enter mainland China on May 4 for the host country's portion of the relay.