Ordinary observers have to ask: Are those North Koreans nuts? This year they have sunk a South Korean warship, made a pudgy, pouty youth into an instant four-star general and heir apparent, held a coming out party for their enriched-uranium nuclear program, and now shelled a nearby island held by South Korea. Who does these things?

China’s best friend does. Under the urban mythical Pottery Barn rule, if you break it, you own it. China took ownership of North Korea’s behavior when it stood between Pyongyang and punishment by the United Nations Security Council for its sinking of the South Korean corvette, Cheonan, last March, with the loss of forty-six lives.

China is the last lifeline to North Korea. It provides or facilitates virtually all the foreign goods needed to sustain the state and its elite. While Beijing probably did not provide the nuclear–related materials displayed by Pyongyang last week and appears to be strictly adhering to the letter of existing UN sanctions, there is nonetheless a brisk commerce between the two communist neighbors. Without it, the North’s regime could barely sustain itself.

China has claimed repeatedly that it supports denuclearization of North Korea and stability in the region. But Beijing has lamely reacted to the shelling of Yeonpyeong Island and the loss of life there by calling for the parties to meet and talk, under the framework of the six-party talks that China hosts. What is more, the Chinese government refuses to use its unique and major influence to leverage a better outcome from the North Koreans. This posture assures more of the same from Pyongyang.

There is a longer running story that weaves these events together. North Korea had a deal with previous–South Korean President Roh Moo Hyun in 2008 to access the waters near the disputed Northern Limit Line west of the demilitarized zone. Current President Lee Myung-bak repudiated that deal, and there has been a series of brief hostilities since then, including the sinking of the Cheonan.

North Korea has also regularly reacted to the large-scale, annual-combined-forces exercises held in the South, and now underway, to deter aggression from the North. Last time, the North fired artillery shells into the sea around the Yeonpyeong Island, and this time they escalated the response to the island itself.

Moreover, there appears to be a pattern in the North’s unique dynastic-succession system of demonstrating toughness during times of transition. This may be done to reflect the priority attached to the military on which the regime depends for survival. It might be intended to spotlight the new leader’s sangfroid. It may also help anneal a beleaguered populace behind an otherwise-challenged regime.

Finally, the North has been seeking a nuclear-weapons capability for over twenty years. It is its only diplomatic card, and the United States and others have been persuaded in the past to pay to hold it, to look at it, to put it in temporary storage, but never to take it away and destroy it. Now, the North looks to open a new bidding game, and has invited a reliable bunch of foreign observers to start the auction.

Options are few, and they put China in the bull’s-eye. Military strikes would enflame the region and not guarantee success against the well-hidden nuclear program. No self-respecting government would engage in diplomacy just to rent the North’s nuclear apparatus for a third time.

Someone needs to put the wood to Pyongyang, and that someone is Chinese President Hu Jintao. China has preferred the stability of the repulsive Northern regime to the goodwill of the people of South Korea, to ultimate reunification of the peninsula, and to peace and stability in the region. But plainly the regime itself is the source of instability, ending the notion that there is a choice between stability and instability. And Pyongyang is directly damaging China’s interests.

This promises to be a very difficult topic during President Hu’s expected January state visit to the United States, if China does not get North Korea’s behavior onto a less provocative and more constructive course. America should strategically, patiently, but urgently press China to assume the responsibility it has taken for the regime in North Korea.