[Jimbuna]

China is key but it is a conflicted party. On the one hand it does not want to see a nuclear-armed North Korea and it has made its view clear to Pyongyang on many occasions.
However, it does not want to see the North Korean regime swept away. This would result in millions of refugees flooding into China and would probably result in a unified Korea very much in the US orbit. This is seen in Beijing as worse than having a difficult nuclear neighbour.
If China were to take the view that the coincidence of a rapidly advancing North Korean nuclear programme and the uncertainties of the Trump Administration's diplomatic capabilities means that there is a very real risk of misunderstanding and catastrophe, then maybe it might bring much greater pressure to bear on Pyongyang.

http://www.bbc.co.uk/news/world-asia-41150291

Catch22