Taiwan will not allow "repeated provocations" from China, the island's defence minister said on Tuesday, as China's foreign minister said Taiwan was the "first red line" that must not be crossed in Sino-US relations.
Tensions over democratically governed Taiwan, which China views as its own territory, have spiked over the past three years as Beijing ramps up diplomatic and military pressure to get Taipei to accept Chinese sovereignty.
China staged war games near Taiwan in August to protest the Taipei visit of then US House Speaker Nancy Pelosi, and Taiwan President Tsai Ing-wen plans to meet current House Speaker Kevin McCarthy in the US in coming weeks, two sources told Reuters.
Speaking to reporters at parliament, Taiwan Defence Minister Chiu Kuo-cheng said he was not aware of a planned meeting between Tsai and McCarthy.
"The Chinese communists use any reason to send troops," Chiu said. "But we won't just say 'bring it on'. We will take a peaceful and rational approach."
Although it hopes this does not happen, Taiwan's military is prepared to fight, he added.
"If the Chinese communists move again, the armed forces' job is to fight," Chiu said. "We won't allow repeated provocations against us. We can't accept that."
Taiwan's government has not announced a Tsai visit to the US, which previously she has made as stop-overs on the way to countries which maintain formal diplomatic ties with Taiwan in Latin America and the Caribbean.
Taking lawmakers' questions, Taiwan Foreign Minister Joseph Wu said it was "inappropriate" to talk about foreign travel arrangements for the president "before there are definite plans".
McCarthy has also not confirmed a meeting with Tsai.
In Beijing, Chinese Foreign Minister Qin Gang said it was "absurd" for US officials to say that Taiwan is not an internal affair of China's.
"The Taiwan question is the core of the core interests of China, the bedrock of the political foundation of China-US relations and the first red line that must not be crossed in China-US relations," he said on the sidelines of China's annual meeting of parliament.
"The US has unshakable responsibility for causing the Taiwan question."
China will keep working for "peaceful reunification", but reserves the right to take all necessary measures, Qin said.
"No one should ever underestimate the firm resolve strong will and great capability of the Chinese government and people to safeguard national sovereignty and territorial integrity."
Taiwan's government strongly disputes China's territorial claims though has repeatedly offered talks with Beijing, and says only Taiwan's people can decide their future.
One of the sources told Reuters that should the US meeting go forward - likely in April - it did not necessarily rule out McCarthy visiting Taiwan in the future.
Four other sources - including US officials and people with knowledge of the US and Taiwan administrations' thinking - said both sides were deeply uneasy that a future visit by McCarthy would severely increase tensions across the Taiwan Strait at a time when the island is preparing for its own presidential election early next year.