China has limited power, and perhaps little desire, to curb North Korea

U.S. President Joe Biden last week asked his Chinese counterpart, Xi Jinping, if he could try to talk North Korea out of a new nuclear weapon test but he
acknowledged that he did not know if China had the capacity to do so.
As unpredictable North Korea builds its arsenal of nuclear weapons and the missiles to fire them across Asia and at the United States, the question of China’s ability to rein in its old ally has taken on particular urgency.
But with tension simmering between the United States and China, especially over Taiwan, the issue may not only be if China has the ability to influence North Korea’s behaviour but to what extent it is in China’s interests to tame a neighbour it has long seen as a useful buffer to the United States.