'Taiwan a red line,' China warns US ahead of Xi-Trump meet

China warned the US over involvement in Taiwan ahead of US President Donald Trump and Chinese President Xi Jinping's meeting. Chinese Ambassador to the US Xie Feng said, "China's ⁠sovereignty, security, and development interests cannot be violated, and four red lines, the Taiwan question, democracy and human rights, development paths and systems, and development rights, cannot ​be challenged."