The longer historical context is that in the 90's the PRNK agreed to hand over their future nuclear power infrastructure to us, in exchange for abandoning a weapons program. Domestic political winds shifted, and the USA chose not to honor the agreement by congress strangling funds. Instead we paid them oil as a substitute. Things broke down further in the Bush 'axis of evil' period.

PRNK's behavior right now seems to be about pushing the USA back to something like the prior agreement, likely because they see the Obama administration as more open to this possibility. Honestly this would probably be a win for everyone, particularly if it included opening up a labor trade between north and south Korea. North Korea is impoverished, but their citizenry is actually quite well educated (if indoctrinated). If economic sanctions were weakened, there's little question that access to north Korean labor would be in high demand globally. There are a lot of challenges to making this happen. Possibly the hardest are social, and will simply take the passing of generations to ease.

There are also probably important PRC PRNK relationship dimensions to all this as well, of which I'm ignorant.