To some extent, I think North Korea is helping do the job for us. One of the issues underlying this discussion is the fact that, for a long time, China has assessed the North Korean threat in a different way than the U.S. and its allies have. When you talk to China about the nature of the North Korean threat, Chinese officials will sometimes turn to me and say, “Oh well, we think the North Korean nuclear missile programs are a real problem, too, because North Korean nuclear testing in mountains towards the Chinese border could create earthquakes, and there could be a potential theft of nuclear material from a North Korean nuclear facility.” If that's the basis of your threat assessment, and you play as important a role as China does in this picture, then we have a problem in terms of actually working on policies that are meant to be based on a common threat picture.
That said, it is becoming increasingly clear that North Korea's behaviour will, indeed, undermine Chinese security. That may be indirect, but the effect will be felt nevertheless. The way that impression is being created at the moment is actually through the U.S. and South Korean discussion over the deployment of ballistic missile defences to South Korea.
China detests ballistic missile defence and U.S. ballistic missile defence architecture. By making clear that the deployment is a direct response to a North Korean threat that is getting out of control and one that is not being actively curbed by China, we are reminding China that its security will be affected by the North Korean nuclear missile programs, even if those missiles aren't pointed at Beijing.