Analysis of the North Korean nuclear test has thus far focused on the predicament the test puts the Obama administration in. The United States is unsatisfied with the status quo, but frustratingly lacks the tools to change the situation. Not enough attention has been paid, however, to the problem that North Korean brinksmanship has created for China.

For some time, China has been content to allow North Korea a degree of latitude, while trying to avoid the worst-case scenarios of war or North Korean collapse. As North Korean behaviour becomes more erratic, the US, South Korea and especially Japan have greater incentive to take aggressive stances that could endanger China's interests in Northeast Asia. The desire to forestall a militarised Japanese response to North Korea could incline China to take a harder stance against North Korea and provide an opening for Sino-American cooperation.

Aggressive North Korean behaviour has unnerved Japan. Last week, prior to the nuclear test, a Liberal Democratic Party panel suggested that Japan should develop the capacity to launch pre-emptive strikes against prospective enemies. This is consistent with the more assertive military stance that Japan has taken in recent years, such as the deployment of warships to the Indian Ocean, and the development of sea-based missile defence. The nuclear test will only give more ammunition to Japanese hawks who wish to alter Article 9, which limits Japan's military to defensive options.

Japan is unlikely to develop its own nuclear forces. As the only people to fall victim to atomic attack, the Japanese have strong cultural reasons to resist nuclear weapons. Moreover, Japan takes non-proliferation very seriously, and has historically been a strong supporter of the international institutions that undergird it.

However, Japan can increase the size, capability and purview of its conventional forces sufficient to make China nervous about its position in east and northeast Asia. Historical concerns aside, Japan has the economic and potential military capability to create problems for Beijing's regional aspirations. The long-term US relationship with Japan serves to keep Tokyo in check, which is fine with China. An aggressive North Korea, however, may make this status quo untenable.

As long as North Korean behaviour was tolerable, China faced a situation in which it would bear many of the costs of a North Korean collapse, while reaping few benefits. The regime's collapse would create massive refugee problems on the Chinese border, with attendant concerns about the proliferation of nuclear and missile technology.

In the future, however, North Korean brinksmanship will become increasingly costly for the Chinese. This creates an opportunity for cooperation between China and the United States.

China's relatively close relationship with North Korea means that Beijing likely has a clearer understanding of the internal situation of the Pyongyang regime than the United States. China probably has a better notion than the US of the balance of power between factions in the succession crisis, and a better idea of which levers to pull in order to strengthen one faction over another.

China and the United States do not have identical interests. It's unlikely that the Chinese have much appreciation at all for North Korean human rights. China also still has some residual concern about the prospect of a unified, democratic Korea, but China has relatively good relations with Seoul, and China-South Korea trade and investment dwarf China's economic interest in North Korea.

China cannot "solve" the North Korean problem on its own. Beijing does not wish to risk a North Korean collapse, and has limited tools with which to affect North Korea policy short of a complete embargo. Nevertheless, the status quo does not work to China's benefit. As long as North Korea continues to test missiles and nuclear warheads, hawkish forces in Japan will grow stronger.

A re-armed, assertive Japan is a bad scenario for Beijing, perhaps even worse than the collapse of the Pyongyang regime. Although the US and China don't have identical interests, they share enough of the same fears to make some cooperation possible. Put bluntly, there is no way to manage North Korea without Beijing's assistance, and Beijing has a strong incentive to facilitate a manageable situation.