In July, after North Korea conducted a series of missle tests, the Bush administration called the acts "unacceptable," but nothing else was done. The big question is, what will it do now that Kim Jong Il has gone a step further and conducted a nuclear test? The response will not only have ramifications in Asia, but it could affect how Iran proceeds with its own nuclear weapon.
The problem is, there aren't any good options for dealing with N. Korea. The dead end six-party talks have obviously been uneffective. At this point, there's no realistic military option. There is talk of going to the U.N. Security Council to impose sanctions, and it appears that one silver lining of N. Korea's test is that the international community is much more likely to support us as we press for such sanctions. But N. Korea earned a charter membership to the "axis of evil" club for a reason, and Kim Jong Il has shown no compunction about starving his own people.
China, the one country that has leverage over North Korea, has consistently protected its neighbor and helped prop up Kim Jong Il's regime, but it called the nuclear test a "flagrant and brazen" violation of international opinion and promised to "resolutely oppose" N Korea's action. It remains to be seen whether that's just all talk.