She was met at the city's airport by James Moriarty, chairman of the board of the American Institute in Taiwan, which manages the unofficial relationship between the US and the island. Several hundred supporters were awaiting Tsai at the entrance to the hotel, flanked by US and Taiwan flags, according to Taiwan's Central News Agency.
US President-elect Donald Trump said in an interview published in The Wall Street Journal that he was not committed to the 1979 agreement with China under which Washington recognized the country's sovereignty over Taiwan. Experts believe that he will use his opposition to nearly four decades of the "one-China" policy as leverage in trade talks with Beijing.
Beijing was also angered by Trump's phone conversation with Tsai last month when she called to congratulate him on his November 8 election victory.
"And why should some other nation be able to say I can't take a call?" Trump questioned in an interview with Fox News. "I think it actually would've been very disrespectful, to be honest with you, not taking it."
Tsai's stay in San Francisco came as Ed Royce, chairman of the US House Foreign Affairs Committee, along with other pro-Taiwan members of the US Congress had introduced legislation that encourages visits between the United States and Taiwan at all levels.
"By encouraging more frequent visits between our two governments, including at the highest levels, we will further strengthen the critical US-Taiwan partnership," Taiwanese media quoted him as saying in a statement.