A special report (January, 2016) by Wikistrat, an online global strategic consultancy, on China's strategic calculus in North Korea explains Beijing's ambivalent response to North Korea's nuclear attics.
The report recommends that the United States should coordinate greater coercive pressure on North Korea among regional stakeholders, including China, South Korea, Japan and other Western allies.
What is missing is the strategic use of economic development to transform the behavior of an essentially insecure regime. What comes to mind is the trajectory of Vietnam from a belligerent Communist hotbed to a modern economic dynamo and a growing ally with the United States. A recent report on North Korea apparently building special economic zones including transport infrastructure should give some food for thought.