According to a recent study if North Korea decides to test its Nuclear weapons the third time there is nothing much the US or other western power can do to stop them. Just like in 2006 and 2009 the event will go unpunished.
Some say that Nuclear weapons are a bargaining chip for the impoverished nation to barter more rice and oil but that is a very simplistic explanation. The reasons go much deeper than that.
To begin with the North Korean regime actually is not a communist regime at all, it is the heir to the Korean Royal line. It is like a dynasty and thus to guard its dynastic heritage nuclear weapons play apart.
Secondly after the fall of the soviet empire and the opening up of Chinese economy leading to a better and friendly relation with the South, North Korea was afraid that it will loose its protection umbrella and thus open to an invasion by the west. In this scenario there was no other alternative for this country other than to develop Nuclear weapons to keep the Americans at bay.
To some extent this has proved quite a dependable strategy and now North Korea is moving ahead in trying to miniaturize the warhead to increase the range of their already substantial cache of missiles. Which incidentally they have sold all over the world in return for rice and other food items. The biggest importer of Korean made missile has been Pakistan and Pakistan has paid the cost by supplying huge amount of Rice.
Unfortunately the solution suggested by the report is knave because it emphasizes that we must put more sanctions and squeeze the North further and accepts that there is no way to stop them but some harsh sanctions might slow them down. Basically the report says wait and watch until North Korea is strong enough to launch an attack on South Korea.I don't think it is the wisest move, instead covert methods must be used to depose the ruling dynasty of Kim from North Korea and free them of this slavery.