For too long, Beijing has coddled, excused, shielded, subsidized, and appeased the indefensible -- Kim Jong-Il's nightmarish regime in North Korea.

China is the key to solving the Korean quandary. The Middle Kingdom is North Korea's largest trade partner, most generous aid donor, and only real friend. Without help from China, North Korea is not viable -- if such an impoverished and benighted nation can be said to be so. In what should be an embarrassment to modern business and political leaders in Beijing, relations between China and North Korea are still conducted by their recondite and fossilized Communist Parties.

Again, the North has crossed the line of civilized behavior -- if indeed it has ever resided on the proper side of that boundary -- by torpedoing a South Korean ship and killing 46 sailors.  This is not new behavior. In October 1983, North Korean agents attempted to blow up South Korean President Chun Doo-Hwan during a wreath-laying ceremony in Burma.  The attempt failed, but killed 21 people, including several of Chun's cabinet.  In the 1970s and 1980s, North Korea kidnapped dozens, if not hundreds of Japanese and South Korean citizens, ripping them from their families to exploit them for their knowledge of the outside world.  In the 1990s, Pyongyang's policies of meeting military needs first and autarky starved more than 1 million North Koreans. Later, North Korea exported nuclear weapons material and technology to Libya and Syria. 

In response to the North's latest atrocity, Chinese Premier Dai Bingguo toured Northeast Asia, urging restraint and maintaining studied neutrality between the aggressor and the aggrieved.  Surely, this is a prelude to asking the United States, Japan, and South Korea to make further concessions to Pyongyang.  At the same time, North Korea seems to be implementing plans for Kim Jong-Eun to succeed his father, perhaps after a period of regency. Undoubtedly, Pyongyang consulted its Chinese patrons on this plan. But rather than perpetuating this monstrous dynasty, Beijing should seize the opportunity for change.

For nearly a decade, the United States has attempted to invest Beijing with a sense of responsibility for solving the North Korea problem. As the country with the most at stake and the most influence over the issue, China should take the lead. While hosting the Six Party Talks on denuclearizing North Korea, China has graciously provided hundreds of lunches to diplomats, but utterly failed to take any of the tough actions necessary to bring about real change in North Korea.

Beijing fears instability, and rightly so.  Military confrontations, refugee flows, and political turmoil are all to be avoided.  But it is time China made a choice between a failed and cruel regime, and a modern, peaceful, and prosperous Korean Peninsula. The United States can stipulate that democratic reunification of  Korea would diminish the need for U.S. ground forces -- and certainly not motivate any movement of U.S. troops toward China's border with Korea.  It would also lessen imperatives for regional missile defenses and closer U.S. alliances with South Korea and Japan -- providing strategic reassurance to Beijing.  Advance planning and coordination on refugee flows, economic dislocations, nuclear proliferation, and security issues would mitigate the dangers of instability. 

On the other hand, if China continues abet North Korea, if it refuses to use its influence in productive ways, it should expect no further help in the form of international ransom payments to Pyongyang.  If Beijing seeks to block effective action by other nations -- as it can do by wielding its veto as a permanent member of the United Nations Security Council -- responding to North Korea's demands should become Beijing's problem exclusively. 

The United States and our allies should then band closer together to contain North Korea militarily -- as we have since the end of the Korean War -- and to defeat and deter Pyongyang's efforts at nuclear and missile proliferation.  We should bring maximum pressure on the North attacking its illicit activities, which range from counterfeiting Marlboro cigarettes, Viagra, and U.S. $100 bills, to drug smuggling and gun running.  We should remorselessly hunt down and confiscate Kim Jong-Il's personal overseas bank accounts, funded by his despotic and criminal activities.  In short, China should know that we will no longer dance to the tune played so long by Pyongyang:  create an international crisis, use that crisis to extract economic and political concessions, and apply those concessions to prop up a bankrupt system.

China is a great power, and still rising.  It is already an economic colossus.  Its people enjoy greater prosperity than ever before because far-sighted leaders accorded them sufficient freedom to succeed.  But if China is to fulfill its enormous promise, Beijing must recognize that its interests no longer lay with the squalid and barbarous dictator ruling a country whose entire GDP and is about equal to China Telecom's revenues. 

The United States must help China to choose between the promise of its future and the worst continuing manifestation of its Communist past.  If we do so, the choice for Beijing should be easy.

William H. Tobey is a senior fellow at Harvard Kennedy School's Belfer Center for Science and International Affairs. Previously, he was Deputy Administrator for Defense Nuclear Nonproliferation at the National Nuclear Security Administration.