Double post to add:
We need China to believe we are working with them on the mutual problem of North Korea.The primary US objective in North Korea is to end the posession of nuclear weapons by a hostile, rogue state. There are three/four primary ways that I can see this happening, in order of idealness, and their associated costs:
I just don't think they really have a problem with North Korea. If any, it is very small.
1: Korean reunification. Lowest probabilty, long shot, all we can do to influence this is to maintain status quo until such a time as the slow evolution of the regime in North Korea continues; this requires whoever Kim Jong-Un installs / has installed for him being more pro-western than the paranoids appointed under Kim Jong-Il and Kim Il-Sung. But it is ideal; it lets South Korea bear the price of rebuilding North Korea, much as West Germany is rebuilding East Germany.
The problem is that both want it, but on their own terms. The North won't compromise, and the South will only compromise a little. Luckily the North won't compromise. There are enough young people in South Korea who want reunification, and aren't old enough to remember the Korean War (or blame it on us?).
2: War, China as ally. If we can pin North Korea between us, that's the ideal military solution. This requires the Chinese government to feel that it is also in the best interests in China; while it cannot be disputed that the China/NK relationship is deteriorating, we would look insincere making that proposal at this time. Building a diplomatic history of working with China on the issue would go a long way.
That's just not going to happen. When it gets to be in China's best interest to war against and occupy North Korea, they will neither need nor want our help. Right now, it isn't in China's best interest to stop North Korea's actions.
3: War, China as neutral party. If we can get China to 'look the other way', North Korea basically becomes Iraq mark 2. We can't afford this option right now. Maybe once we're wrapped up in Iraq and Afghanistan, but the expense and difficulty of nation building has already left a very, very bitter taste in the electorates' mouths. We have to, again, build the case that it's in China's interest to look the other way. Working with China over the containment issues, again, goes a long way.
Again, not going to happen. North Korea is a buffer and protected state. They will not allow anyone else to remove the current regime and remove North Korea's usefulness to China. It is not going to be in China's best interests, ever given to two regimes in question.
4: War, China hostile. Hahahahahahahahahahahahahahahahahahaha. If China decides that it's in their interest to fight on behalf of North Korea, it's either a long war of hideous attrition, and massive economic devestation on both sides, or a very short one with the exchange of radioactive craters. I fully expect that once we're in an all-in war in Asia, Iran is going to cackle with glee and try something stupid, and we'll have to multi-front it with NATO. Giving them the finger over the back channels and provoking North Korea is how we can make it happen, though. It's not a certainty, because of the extreme expense to China, but it's a possibility, and it's ultimate disaster scenario 1. But there won't be a North Korea to speak of afterwards.
If we can limit it to the Korean peninsula, we might limit it to conventional weaponry between us. The North Koreans won't see it that way. We would still find a real problem in defending against a massive Chinese army. And I doubt China would accept defeat above the 38th parallel, maybe not even below it, so they will always reserve the right to go beyond conventional weaponry. A scenario to be avoided if at all possible.
5: Of course, ultimate disaster scenario 2 is the complete collapse of the North Korean regime and the sale of nuclear devices to Iran or independent agents by ex-DPRK officers looking for a quick buck.
China isn't likely to allow that to happen. They are friends with North Korea and want that buffer and deniability for whatever they may encourage the North to do. They are friends with Iran, but will have to make some economic concessions to other western countries, or plan on world war. They might chance it if they think they can let the rest of the world wear itself down, then pick the most advantageous side to support, at a great cost to that side. They have to be sure they can survive economically until they think it advantageous to intervene somewhere. They can use a military buildup to help their own economy. Not a good scenario for anybody else.
