Here is an interview with former U.S. Assistant Secretary of Defense Joseph Nye (whom I and many thought would become the US Ambassador to Japan). Dr. Nye says that the United States must confer with China in preparation for collapse of North Korea. Read the rest of the Yomiuri interview below:

"Harvard University Professor and former U.S. Assistant Secretary of Defense Joseph Nye recently gave an interview to Global Viewpoint, a weekly commentary and feature interview service, which has a special contract with the Yomiuri Shimbun. In the interview, Nye, envisaging the collapse of North Korea, presented his opinion that the United States should confer with China on a response to such a situation.-- Such steps as ship inspections may be able to block North Korea's nuclear proliferation. But wouldn't they lead to the acknowledgement of North Korea as a nuclear state?"North Korea has exploded two nuclear bombs, so in short, it is a de facto nuclear state. Nevertheless, the United States and its allies have no intention of giving up their long-term policy goal of denuclearizing the Korean Peninsula.""North Korea is also aiming to conduct bilateral talks with the United States to obtain a guarantee from the United States that it will not attack the DPRK as a legitimate nuclear state. The North is hoping to elevate and strengthen the position of its administration through nuclear tests, but that is a pipe dream."-- What must be done to have the North abandon its nuclear program?"It is now a cliché to say that North Korea will change if China applies greater pressure. China is hoping for the denuclearization of North Korea. At the same time, it does not want to see the North collapse in a way that throws its border with China into chaos. Because of those two incongruous objectives, China has been hesitant to wield its influence on North Korea.""As such, it is advisable for the United States to begin privately discussing responses with China, envisaging the collapse of North Korea. The United States should confer with China on, among other matters, whether U.S. forces should go all the way to Yalujiang and how the United States and the international community should support China in case North Korean refugees flock to China."-- Given North Korea's moves, there are calls in Japan for possessing enemy-base strike capabilities and arming itself with nuclear weapons."I don't think Japan's nuclearization is inevitable. After all, Japan has long had the capacity to possess nuclear weapons at any time.""Despite that, Japan has decided not to go nuclear. That is because 80 percent of its people are against it and also because nuclearization would eventually damage the security of Japan.""Of course, the situation would drastically change if the United States ended its alliance with Japan or if the U.S. nuclear deterrent that covers Japan lost its credibility. In such a case, Japan might go nuclear."-- Japan is skeptical that the United States would sacrifice Los Angeles to defend Tokyo in a contingency."During the Cold War, Berlin was protected from the threat of the Soviet Union. The dilemma of sacrificing Los Angeles for Tokyo is false. Rather than sacrificing Los Angeles, it would involve accepting a small amount of risk in exchange for the security and stability of East Asia. Is it certain that the United States would do that? The answer is 'yes.'"You can read the Brookings North Korea Collaspe Scenarios here.