Assistant Secretary of State Christopher Hill recently told the Senate Foreign Relations Committee that the United States did not believe that China was putting sufficient pressure on North Korea to end its nuclear weapons program.

Washington continues to believe, as it has since the North Korean crisis began in late 2002, that China is the key to solving the impasse. 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 likely to be disappointed yet again. Already, there is noticeable frustration in Washington that China has not done more to pressure its neighbor. That disappointment may well grow in the coming months. Beijing has made it clear that, although it hopes that Pyongyang returns to the six-party talks and negotiates an end to its nuclear program, China will resist imposing economic sanctions (much less taking stronger measures) against its recalcitrant neighbor. Beijing's position is strongly supported by America's nominal military ally, South Korea.

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 restoring 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, China has worried that the North Korean regime might implode, much as 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 -- probably with a continuing U.S. troop presence on the Peninsula. A North Korean collapse might also lead to a massive flow of refugees into China, with all of the social and economic dislocations that could create.

The overriding objective of keeping North Korea as a viable country places a definite 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 terminate its nuclear weapons program -- or at least put it 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 frosty or nonexistent 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. Of course, it is possible that Kim's regime may push even its tolerant Chinese ally too far. A North Korean nuclear test, for example, might force Beijing's hand despite the risks entailed in adopting coercive measures toward Pyongyang.

Short of such a dramatic development, though, U.S. officials are making a serious miscalculation if they are counting on China to "deliver" a non-nuclear North Korea. Even worse, the growing bitterness at China's lack of cooperation could seriously damage U.S.-Chinese relations, and that would have grave consequences for the entire East Asian region.

Ted Galen Carpenter, vice president for defense and foreign policy studies at the Cato Institute, is the author of 6 books and the editor of 10 books on international affairs. His most recent book, coauthored with Doug Bandow, is The Korean Conundrum: America’s Troubled Relations with North and South Korea.