The primary purpose of Secretary of State Colin Powell’s recent trip to East Asia was to forge a solid diplomatic front among North Korea’s neighbors against Pyongyang’s revived nuclear weapons program. Powell and other members of the Bush administration believe that China is by far the most crucial participant in that coalition. Indeed, the administration apparently expects China to exert whatever diplomatic and economic pressure is needed to get North Korea to abandon its nuclear ambitions.

U.S. leaders are almost certain to have their hopes dashed. Powell has already expressed disappointment that China has not done more to pressure its neighbor, and that disappointment is likely to grow in the coming months.

Washington overrates both Beijing’s willingness and ability to get North Korea to remain non-nuclear. True, Chinese leaders may be willing to exert some diplomatic, and perhaps even economic, leverage on Pyongyang to achieve that goal. Although a few Sinophobes in the United States charge that China is in league with the North Koreans and would not mind seeing a nuclear-armed North Korea, most evidence suggests that Beijing is not eager to see nuclear weapons introduced on the Korean Peninsula. Among other drawbacks, such a development would increase the chance that Japan would respond by building a deterrent of its own, and a nuclear-armed Japan is the last thing China wants to see.

But while maintaining the non-nuclear status quo on the Korean Peninsula may be a significant Chinese objective, it is not the most important one. Beijing’s top priority is to preserve the North Korean state as a buffer between China and the U.S. sphere of influence in Northeast Asia. As North Korea’s economy has languished in recent years, resulting in mass famine, China has worried that the North Korean regime might implode, much as the East German system did in 1989. Such a development would lead to the sudden emergence on China’s border of a unified Korea allied to the United States. It might also lead to a massive flow of North Korean refugees into China.

The overriding objective of keeping North Korea as a viable country places a distinct limit on the amount of pressure that Beijing is willing to exert on Pyongyang. In theory, China might be able to use its economic leverage as North Korea’s principal source of energy and other vital commodities to compel Kim Jong Il’s regime to put its nuclear weapons program back into the deep freeze. In reality, though, China fears the possible consequences of using that leverage.

And as far as diplomatic influence is concerned, the United States overrates Beijing’s clout. China may be North Korea’s closest ally, but that is only because most other countries (with the partial exception of Russia) have utterly frosty relations with the reclusive Stalinist state. The North Korean elite is not especially fond of China. In addition to the wariness with which a small state typically regards a much larger neighbor, Pyongyang considers the Beijing government a communist apostate for its extensive flirtation with market-oriented economic reforms and its tolerance of a considerable amount of social pluralism for the Chinese people. The North Koreans may listen to China’s diplomatic message that it is dangerous and counterproductive to pursue the nuclear option, but it is not at all certain that they will heed that message.

In short, if U.S. officials are counting on China to “deliver“a non-nuclear North Korea, they are making a serious miscalculation. Beijing will probably try to be helpful on the issue, but its willingness and ability to influence Pyongyang are quite limited.