Chinese regulators said on Thursday that North Korean companies in China, including those that have joint ventures with Chinese firms, must shut down within less than four months, a signal of growing tensions between the two countries over Pyongyang's nuclear and ballistic missiles programs. The move comes amid heavy pressure from the Trump administration, which has made the North Korean nuclear issue the cornerstone of its policy in Asia. President Trump and members of his administration have repeatedly signaled that the US depends on China to enforce international sanctions on North Korea in an effort to curb Pyongyang's nuclear ambitions....