there are no appealing options in this case. It seems clear that the co-operation, or at least acquiescence of the Chinese government is going to be needed, and that any military option raises a severe risk of an attack on South Korea and perhaps Japan. The most promising solution is one where China applies the pressure required to force the abandonment of North Korea’s nuclear program and its missile development.
Kristof makes the same point, observing that without Chinese support, sanctions will mean nothing.
Getting China to do something would be really difficult and would require the expenditure of a huge amount of diplomatic effort and political capital. It would not, however, be beyond the power of a determined US government, willing to put in an all-out effort to rally international support for a campaign against an evil dictator with real weapons of mass destruction, while applying a policy of containment to less immediate threats.
(As an aside, it’s often argued that the example of North Korea proves the good sense of moving pre-emptively. But in this case the US has tried eliminating the threat by force. General Macarthur’s army entered Pyongyang in 1951 before retreating when the Chinese entered the Korean War. So, the question to the advocates of pre-emption is – should the US have attacked China as Macarthur wanted? If not, when should the policy of pre-emption have been resumed?).