Chinese President Xi Jinping warned his US counterpart Joe Biden not to cross Beijing’s “red line” over the island of Taiwan in Monday’s summit meeting between the two, state media reported….The Taiwan question is at the very core of China’s core interests, the bedrock of the political foundation of China-U.S. relations, and the first red line that must not be crossed in China-U.S. relations,” Xi was reported to have told Biden, state news agency Xinhua said, following the over three-hour talks.