Taiwan's President Tsai Ing-wen speaks on the phone with U.S. president-elect Donald Trump at her office in Taipei, Taiwan, in this handout photo made available December 3, 2016. Taiwan Presidential Office/Handout via REUTERS

BEIJING (Reuters) - China’s Foreign Ministry said on Saturday that it had lodged a protest with the “relevant side” in the United States after President-elect Donald Trump spoke by telephone with the president of self-ruled Taiwan, Tsai Ing-wen.

The “one China” principle is the political basis of the China-U.S. relationship, the ministry added, urging the “relevant side” to uphold this policy and carefully handle the Taiwan issue to avoid unnecessary disturbances in ties.