US president-elect Donald Trump is unapologetic about the storm over his decision to speak on the phone with Taiwan's leader - a breach of long-standing tradition that risks angering China.
The US cut diplomatic ties with Taiwan in 1979, but has maintained close unofficial relations and a commitment to support its defence.
Trump's conversation with President Tsai Ing-wen drew an irritated, but understated response from China, with foreign minister Wang Yi saying the contact was "just a small trick by Taiwan" that he believed would not change US policy towards Beijing.
Chinese officials said they lodged a complaint with the US and reiterated a commitment to seeking "reunification" with the island, which they consider a renegade province.
Trump has since complained about the backlash the call has received.
Since 2009 the Obama administration has approved $14 billion (£11bn) in arms sales to Taiwan.
This call was the starkest example yet of Trump flouting diplomatic conventions since he won the election. He has apparently undertaken calls with foreign leaders without guidance customarily given by the State Department, which oversees the country's diplomacy.
"President-elect Trump is just shooting from the hip, trying to take phone calls of congratulatory messages from leaders around the world without consideration for the implications," said Bonnie Glaser, senior adviser for Asia at the Centre for Strategic and International Studies in Washington.
Over the decades, the status of Taiwan has been one of the most sensitive issues in US-China relations. China regards Taiwan as part of its territory to be retaken by force, if necessary, if it seeks independence and would regard any recognition of a Taiwanese leader as a head of state as unacceptable.
Taiwanese newspapers ran banner headlines on Sunday about the call, with two noting on their front pages that Trump referred to Tsai as "the president of Taiwan" - something which would signal a huge shift in American policy and infuriate China.
But Douglas Paal, a former director of the American Institute in Taiwan, which unofficially represents US interests in Taipei, said it was too soon to judge whether Trump was going to lead that shift, or if the incident was just a "complicated accident".