For his part, Kim is able to sleep at night because he knows that those on whom his safety depends have a stake in his well-being. If times get tough and money grows tight, however, those people will begin to feel the pinch, the circle of beneficiaries in the spoils system will become smaller and Kim will steadily grow less secure. What Kim has to fear is not a popular uprising but a palace coup. The North's people are too beaten down and weak to stage a revolution, but Kim knows that a handful of disgruntled generals or disaffected party leaders could bring a sudden end to his brutal reign.

With the help of allies such as Japan and Australia, Washington has already taken steps to disrupt North Korean arms sales, counterfeiting and drug smuggling. Last year the United States also began to go after the network of financial institutions through which dollars flow back to Pyongyang. These initiatives need to be greatly intensified and coupled with other measures to constrict Kim's dollar lifeline.

Recently announced U.N. sanctions are a step in the right direction, but they are not enough. China must take responsibility for preventing illicit activities on or through its territory, and both China and South Korea need to ensure that whatever assistance they provide the North's people cannot readily be converted to cash by Kim and his cronies.

Seoul and Beijing have thus far been reluctant to take such steps for fear that they might provoke Kim or cause the North to collapse. The time for hesitation has long since passed. Kim may test more nuclear devices and ballistic missiles, but he is not about to attack the South or make other moves that would bring crushing retaliation. As for the danger of regime collapse, the "Dear Leader" has even more reason to fear it than do his neighbors. It should be made clear to all, including Kim, that the objective of ratcheting up financial pressure is not to topple him but to squeeze him until he chooses to abandon his nuclear ambitions.

Getting China and South Korea on board will not be easy. Both may prefer feeble gestures and empty rhetoric to tough, united action. If Seoul and Beijing remain reluctant, however, they must be made to understand that they are endangering not only the security and stability of Northeast Asia but also their future relations with the United States. The weapons Kim is perfecting could one day lay waste to an American or Asian city. Passivity in the face of this threat will lead to sharp questions from Congress and the public about the continuing value of the U.S. alliance with South Korea, to say nothing of China's supposed status as a "responsible stakeholder" in the international system.

Absent sufficient cooperation, Washington will have to weigh other risky measures. Among these are a stop-and-search blockade of North Korea's ports, secondary sanctions against companies that continue to trade with it, and aggressive criminal proceedings that could entangle individuals and institutions in other countries, including China, with unforeseeable but potentially far-reaching diplomatic and economic consequences.

---

Aaron L. Friedberg is a professor at Princeton University's Woodrow Wilson School and a former deputy assistant for national security affairs to Vice President Dick Cheney.