Taiwan President Tsai Ing-wen's meetings with two senior Republicans during a stopover in Houston, Texas, have sparked opposition from China, which urged the US to abide by the "one China" policy.
Ms Tsai, who was en route to Central America to visit Honduras, Guatemala, El Salvador and Nicaragua, met Texas Senator Ted Cruz and Texas Governor Greg Abbott during a transit stop on Sunday.
As she arrived in Honduras yesterday, news of the meeting broke, with Mr Cruz saying in a statement that he and Ms Tsai discussed arms sales, diplomat exchanges and economic relations and that he hoped to increase trade between Texas and Taiwan.
Asked to comment on the meeting, Chinese Foreign Ministry spokesman Lu Kang said: "We are firmly opposed to the Taiwan leader's engagement with US officials under the pretext of transit, and her attempt to undermine China-US relations."
Mr Lu urged the US and relevant parties to "strictly abide" by the "one China" policy and to "appropriately handle the Taiwan issue so as to prevent hurting the big picture of Sino-US relations and the peace and stability of the Taiwan Strait".
But a newspaper linked to the Chinese Communist Party took a more strident tone, warning in a commentary yesterday that China would "take revenge" if US President- elect Donald Trump reneged on the "one China" policy.
Saying that "there is no room for bargaining", the nationalistic Global Times added: "(But) in case he tears up the 'one China' policy after taking office, the mainland is fully prepared. Beijing would rather break ties with the US if necessary. We would like to see whether US voters will support their president to ruin Sino-US relations and destabilise the entire Asia-Pacific region."
Taiwan's presidential office remained mum about the meetings, saying only that Ms Tsai spoke with "friends" during her stopover.
While it is not unusual for Taiwan's leaders to meet lawmakers during stopovers in the US, Ms Tsai's nine-day trip to Central America is being closely watched by China, which is deeply suspicious of her and her independence-leaning Democratic Progressive Party.
An unprecedented phone call between Ms Tsai and Mr Trump last month stoked tensions with China. Mr Trump further angered Beijing when he questioned the need for the US to continue the decades-old policy of recognising Taiwan as a part of "one China".
Taiwan is grappling with the fallout. China has imposed limits on the number of Chinese visiting Taiwan and is seeking to reduce the island's presence in international forums. Most recently, West African nation Sao Tome and Principe switched diplomatic recognition to Beijing, further shrinking Taiwan's circle of diplomatic allies to 21, including the four Central American nations Ms Tsai is visiting.
Mr Cruz said some members of Congress received a letter from the Chinese side asking them not to meet Ms Tsai.
"The People's Republic of China needs to understand that in America, we make decisions about meeting with visitors for ourselves," he said. "This is not about the PRC. This is about the US relationship with Taiwan, an ally we are legally bound to defend."
Political analyst Yen Chen-Shen does not expect China to take any punitive action, saying: "It is normal that China protests but it knows that it is not out of the ordinary for US local congressmen to meet Taiwan's leaders. Beijing is just going to wait and see until Mr Trump is in office."