Donald Trump's challenges to China on trade and Taiwan are rattling American companies who have long benefited from stable relations between the two countries.

U.S. President-elect Donald Trump questioned whether the United States had to be bound by its longstanding position that Taiwan is part of "one China" and brushed aside Beijing's concerns about his decision to accept a phone call from Taiwan's president.

U.S. President-elect Donald Trump's phone conversation with Taiwan President Tsai Ing-wen on Friday, which prompted a diplomatic protest from China, was simply a "courtesy call," Vice President-elect Mike Pence said on NBC on Sunday.