No American president or president-elect has spoken to a Taiwan leader since 1979. So the surprising telephone call between Taiwan leader Tsai Ing-wen and US President-elect Donald Trump on Friday provides further proof that the incoming US leader is determined to defy convention both domestically and in his foreign relations.

The three joint communiques the United States signed with China in 1972, 1978 and 1982, no matter read separately or as one, all explicitly say the US recognizes Taiwan as part of China and the People's Republic of China as the sole legal government of China.

Even though the world had got used to Trump's wild, and sometimes offensive, remarks during his presidential campaign, it would be unreasonable to tolerate his disregard of the US' commitments to the three monumental documents, which lay the political foundation for China-US ties.