Kurt Campbell, the US deputy secretary of state, said China is being kept in the dark about the friendship between Kim Jong Un and Vladimir Putin

Over the past decade, China has grown increasingly concerned about its waning leverage over North Korea and inability to restrain Pyongyang’s nuclear ambitions. These worries have only intensified with North Korea’s dramatic tightening of ties with Russia this year.

China is uneasy about North Korea's ties with Russia, fearing it may embolden Pyongyang against its interests amid regional tensions.