China vows 'vigorous' response to US visit by Taiwan vice president

China's foreign ministry has criticised a brief US visit by Taiwan vice president William Lai, saying he was a separatist and "troublemaker through and through" and Beijing would take strong steps to protect its sovereignty. Lai, a frontrunner to be Taiwan's next president at elections in January, arrived in New York late on Saturday for what is officially a transit on his way to Paraguay for the inauguration of its president. China, which claims democratically governed Taiwan as its own territory, has repeatedly denounced Lai's trip. It includes another stopover in San Francisco on Wednesday on his way back to…