China’s Foreign Ministry has lodged an official complaint with the U.S. over President-elect Donald Trump’s phone conversation with Taiwan’s president, a move which went against decades of diplomatic protocol. Trump’s controversial decision to accept a call from Taiwanese President Tsai Ing-wen sparked major controversy Friday, as the U.S. has viewed Taiwan, a renegade province, as part of China since 1979, with no formal diplomatic relations between the two. Trump shrugged off criticism, writing on Twitter that the Taiwanese side had called him and he'd simply responded. A Taiwanese official later said the talk was prearranged, however. Chinese Foreign Minister Wang Yi labeled the phone conversation a “shenanigan from the Taiwan side,” hinting that it could damage U.S.-China relations. A statement Saturday from China's Foreign Ministry spokesman Geng Shuang echoed that sentiment. “I must point out that there is only one China in the world and Taiwan is an inseparable part of the Chinese territory ... We urge the relevant side in the US to adhere to the 'one China' policy, abide by the pledges in the three joint China-US communiques, and handle issues related to Taiwan carefully and properly to avoid causing unnecessary interference to the overall China-U.S. relationship,” the statement said.