Last week, Chinese General Zhu Chenghu stated that China “will have to modernize its nuclear arsenal” as U.S. missile defense “may reduce the credibility of [China’s] nuclear deterrence.” Even if the statements reflected reality, it should encourage the U.S. to strengthen its defenses.

U.S. missile defenses are still woefully inadequate to defend against the Chinese missile arsenal. The U.S. systems are meant to intercept the far more simple missiles of rogue nations—mainly North Korea and Iran, neither of which has yet demonstrated a truly intercontinental-range ballistic missile, much less one equipped with penetration aids or multiple warheads.

Beijing did not recently come to the conclusion that, due to U.S. missile defense plans, it must build up its nuclear arsenal. China maintains a nuclear force that can reach most of the world and has been modernizing its force at a steady pace for at least a decade. China likely has 1,600–1,800 nuclear warheads. Moreover, General Zhu himself indicated in 2005 that China might use nuclear weapons in response to conventional attacks against Chinese territory or even Chinese military forces, such as aircraft or a warship.

China has also been working very hard on its missile program, which could be used to deliver its nuclear weapons. It is willing to do this even at the price of international outrage, as proved by the successful ASAT test in 2007.

In December 11, 2009, Beijing revealed it had spent the last 25 years working on a massive 3,000-mile underground tunnel system. This system could potentially be used to house (and hide) nuclear and missile forces.

But why would the general oppose missile defense in Asia and use U.S. missile defense as a pretext for building up the Chinese nuclear arsenal? Well, it’s working for Russia.

Chinese state-owned media has pointed to Russia’s objections over U.S. missile defense deployments in Eastern Europe as behavior worth emulating. Russia leverages objections to missile defense to get concessions out of the U.S. Demonstrating President Obama’s willingness to concede U.S. missile defenses, the President was caught by an open microphone with then-Russian President Dmitry Medvedev, in which President Obama said he’d have more “flexibility” after the November presidential election on missile defense. Perhaps the Chinese also want to take advantage of President Obama’s “flexibility” if he wins another term.

But even if China is now feeling threatened by U.S. military systems, and therefore believes there is a need to counter them by building up offensive weapons, this should reinforce the need for U.S. defenses.

The missile defenses currently deployed and the ones the U.S. is planning to deploy are purely defensive in nature and designed to protect the U.S. and its allies, including South Korea and Japan, from weapons that have already been launched from hostile countries. To fail to build these defenses is to purposefully leave Americans and our allies totally vulnerable to incoming—and possibly nuclear-armed—ballistic missiles. Even if China doesn’t have the intent to pose this threat to the U.S. or our allies in Asia, North Korea certainly does.

The U.S. should defend against rogue states even if China would rather we didn’t. Moreover, if China is determined for its nuclear weapons to have a free ride to American military bases and cities, or those of our allies—which by all accounts they do—it would be foolhardy for U.S. policymakers to do anything but build stronger and more robust defenses.