Taiwan's new de facto ambassador to the United States, Alexander Yui, arrived in Washington on Monday, according to a tweet from a U.S. official, taking up Taipei's highest-profile diplomatic post at a sensitive time ahead of the island's election in January. Taiwan officials have warned that China is trying to sway the democratically governed island's Jan. 13 presidential and legislative election, which is happening as Beijing ramps up military and political pressure to try to force Taipei to accept its sovereignty. Despite a lack of formal ties, Washington is Taiwan's main diplomatic backer and arms supplier, and U.S. President Joe Biden has asked Chinese leader Xi Jinping to respect Taiwan's electoral process. The American Institute in Taiwan's (AIT) managing director, Ingrid Larson, welcomed Yui upon his arrival to Washington on Monday, AIT chair Laura Rosenberger said in post on X, formerly known as Twitter. "Representative Yui is a friend we know well, and with his significant experience, we're confident our partnership will continue to grow and strengthen!" said Rosenberger, who leads AIT as it manages unofficial U.S. ties with Taiwan. The Taipei Economic and Cultural Representative Office (TECRO), Taiwan's de facto embassy in Washington, did not respond immediately to a request for comment. Taiwan late last month appointed Yui, formerly Taiwan's representative to the European Union, as the envoy to Washington, replacing Hsiao Bi-khim who vacated the post to be the vice-presidential running mate for current Vice President Lai Ching-te. Lai and Hsiao, from Taiwan's ruling Democratic Progressive Party, are leading in the polls, but China views them as separatists and has rebuffed Lai's offers of talks. U.S. officials have been careful to avoid taking a public position on candidates in Taiwan's election, but have said stability in the Taiwan Strait is crucial and that Chinese military coercion around Taiwan ahead of the election is dangerous and provocative. The Biden administration also has sought to stabilize rocky bilateral relations with Beijing, and has repeatedly said it is not supportive of Taiwan independence. Political and military analysts widely expect that Beijing will continue to carry out military patrols and drills around the election and in the run-up to the inauguration of the eventual winner to dissuade any moves that China would view as supporting Taiwan's independence.