Donald Trump reckons himself a master of the high-stakes gamble. Over the weekend, the US president-elect questioned whether his administration would respect the “One China” policy, by which the US acknowledges just one legitimate Chinese government. This prompted a robust response from Beijing. Any spat risks hurting Taiwan businesses — and US interests as badly.

Until Mr Trump’s victory in November, China’s government was accepted as the one that rules on the mainland. Earlier this month the president-elect broke with protocol by accepting a phone call from Tsai Ing-wen, the president of Taiwan. On that occasion, China reacted with restraint, protesting directly to Washington. Like Mr Trump’s posturing, Beijing’s reaction has escalated. On Monday, China hit back, its foreign ministry denouncing Trump’s comments.

US dependence on Taiwanese manufacturing runs deep. Over the years, as technology companies such as Intel and Dell have invested less in production, they have outsourced to Taiwanese manufacturers. Nor does their dependence stop at Taiwan’s shores. As relations between China and its “renegade province” have thawed, Taiwanese companies’ mainland-based facilities have grown. As a result Apple, dependent on the semiconductor maker TSMC and manufacturer Foxconn (listed in Taiwan as Hon Hai), relies on mainland China too. At end of 2015 three quarters of Foxconn’s fixed assets were across the straits.