North Korea

`We will give the nations with the closest ties to North Korea -- China and South Korea -- a framework to use their leverage to pressure Pyongyang and persuade its regime to change course,'' Bush said. October 14,bloomberg

Why China and South Korea?
The rates of North Korean trade with China and South Korea are 38,9％, 26% respectively. That of the trade with Japan is just 4.8%.
The Japan's embargo has little effect if China and South Korea do not corporate.　依存症
The best way to put China into motion is to insinuate that international community will boycott Beijing olympic if China will not take the matter seriously.　
How about South Korea? ーーーーforget it, South Korea is not the player in international theatre, and she will do whatever she wants to do anyway.