Secretary of State John Kerry with Chinese Premier Lie Keqiang at a meeting in Beijing. (AP Photo/Jason Lee, Pool)

In mid-March, when the United States first announced that it would dramatically expand missile defense batteries in Alaska and California, the explanation puzzled a number of analysts. According to Defense Secretary Chuck Hagel, the $1 billion program would be a defense against North Korea, although the country's rogue missile program has no demonstrated capability to reach anywhere near the United States, much less land with real accuracy.

Analysts, accustomed to guessing over Pyongyang's intentions and capabilities, were left guessing about Washington. Pentagon-watchers smelled another overpriced, underperforming boondoggle. North Korea analysts scoffed at an American overreaction. Some wondered if Hagel might be using North Korea's recent provocations as a polite excuse for a defense program that was actually aimed at China's growing power – something that Beijing itself seems to suspect.

Whatever the original purpose, Secretary of State John Kerry seemed to find a new use for the not-always-successful missile defense batteries during his recent visit to Beijing, where he offered to cut back U.S. missile defense in the Pacific if North Korea abandoned its nuclear program.

Kerry's offer is probably not going to change Pyongyang's nuclear calculus any more than past U.S. efforts have. Still, it's a particularly creative approach, and maybe one with a slightly higher degree of success than normal, for two reasons.

First, the offer likely appeals more to China than it does to North Korea. Pyongyang loves to threaten the United States but has no real interest in striking American soil, which could lead to the Kim regime's destruction; California missile defense, then, probably doesn't bother North Korea so much. Beijing, however, seems to see the batteries as part of a larger U.S. effort to encircle and isolate China. So Kerry's offer may give China a stronger incentive to pressure their North Korean ally to curb its nuclear program.

That gets to the second reason this could be a canny plan. The United States has few real sticks to use to deter North Korea, so it has to rely on giving the nation concessions in exchange for (usually short-lived) good behavior. It's a familiar and distasteful pattern: North Korea does something provocative, the United States and other countries offer food aid or some other goody to calm it down. But China, an important if increasingly impatient sponsor of the North Korean regime, has lots of ways to punish Pyongyang -- for example, by withholding assistance or tamping down on cross-border trade.

So, by offering to withdraw some missile defense if North Korea rolls back its nuclear program, Kerry has given China a good reason to do what the United States can't really do on its own: penalize North Korea for its bad behavior.

There's no guarantee that China will follow through on this, as it still appears to believe that supporting North Korea is its least bad option. And it's difficult to imagine that even a severe Chinese punishment could drastically change North Korea's calculus. After all, Pyongyang did not open up to the world even after Russia's early-'90s decision to withdraw aid led to a famine that killed thousands, perhaps millions, of North Koreans.

If nothing else, Kerry's missile defense gambit is an attempt to turn the tables on North Korea, to reverse the usual dynamic in which North Korea threatens the world until the world rewards it for quieting down. Maybe, just maybe, the United States has finally found something that will effectively pressure a Pyongyang regime that has long seemed immune to American coercion.