Trump agreed to honor the United States' "One China" policy during a phone call with Chinese President Xi Jinping, as he took steps to improve ties after angering Beijing by talking to Taiwan's leader.

The warning came only hours after Taiwan's president Tsai Ing-wen made a controversial stopover in Houston despite Beijing asking Washington not to allow her into the U.S.

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.

President-elect Donald Trump continued to use Twitter Sunday to defend his engagement with the leader of Taiwan, a breach of U.S. diplomatic protocol.

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.

Donald Trump is unapologetic about roiling diplomatic waters with his decision to speak on the phone with Taiwan's leader, a breach of long-standing tradition that risks enmity from China.

China lodged a diplomatic protest after Donald Trump spoke by phone with President Tsai Ing-wen of Taiwan, but blamed the self-ruled island.

President-elect Donald Trump spoke Friday with the president of Taiwan, a move that will be sure to anger China.