Taiwan's President Tsai Ing-wen arrived in New York on Wednesday for a stopover amid threats from China that there would be retaliation if she met with US House Speaker Kevin McCarthy.
Tsai is en route to Central America, where she will meet with leaders of Guatemala and Belize, two of the few countries that recognize Taiwan diplomatically.
She will stay in New York until Saturday and will also visit Los Angeles on her return from Central America. Tsai is expected to meet McCarthy in California, although this is not officially confirmed.
Meanwhile, one of Tsai's most prominent domestic opponents, former Taiwanese President Ma Ying-jeou, embarked on a trip to China on Wednesday, the first such visit by a former Taiwanese leader.
China vows to retaliate
Beijing has warned against any meeting between Tsai and McCarthy and vowed to take "resolute measures to fight back" if it goes ahead.
Xu Xueyuan, the charge d'affaires at the Chinese embassy in Washington, said she had spoken directly to US officials numerous times and warned them that Tsai's trip would violate China's core interests.
"We urge the US aside not to repeat playing with fire on the Taiwan question," she told reporters, alluding among other things to last year's visit to Taiwan by then House Speaker Nancy Pelosi.
Recent visits by a Czech delegation and a German minister were met with rebukes from Beijing.
US urges China not to act aggressively
Pelosi's visit triggered an angry response from Beijing, with the Chinese military conducting drills at an unprecedented scale around the island.
This time round, the United States said China should not use Tsai's stopover as an excuse to act aggressively near the Taiwan Strait.
China claims the island as part of its territory, and vows to reunite it with the mainland, even by force if necessary. And Beijing opposes official ties betweeen Taipei and foreign governments.
Tsai's trip follows Honduras's decision this month to establish diplomatic relations with Beijing, leaving Belize and Guatemala among the just 13 countries that have official ties with Taipei.
Diplomatic battle between Taipei and Beijing
China has increased investment in Latin America, a key diplomatic battleground between Taipei and Beijing.
Taiwan accused China on Sunday of using "coercion and intimidation" to lure away its allies after Honduran Foreign Minister Enrique Reina and his Chinese counterpart Qin Gang officially launched relations in Beijing.
Meanwhile, the Honduran Foreign Ministry said on Twitter that President Xiomara Castro will travel to China "soon," without providing a date for the trip.
The move continued a trend in Latin America, with Nicaragua, El Salvador, Panama, the Dominican Republic and Costa Rica all switching diplomatic recognition to Beijing in recent years.
In addition to Guatemala and Belize, Taiwan still has official ties with a handful of countries in Latin America and the Caribbean, including Paraguay and Haiti.