The Trump administration assuredly deserves credit for negotiating a series of UN resolutions imposing unprecedented economic sanctions against North Korea for its nuclear and missile tests. But these sanctions are a race against time. Can North Korean strongman Kim Jong-un develop a credible threat of nuclear-armed ICBMs before these sanctions put enough pressure on his regime to force him to abandon his nuclear program?

After all, the North Korean dictator’s tolerance for economic pain probably exceeds the pain that UN sanctions can inflict in the short run. Even if the CIA’s Korea Mission Center is correct that Kim is rational, a ruthless rationality can be quite irrational to the civilized world. Moreover, the North Korean leader no doubt recognizes that nuclear-armed ICBMs are a game changer since a U.S. president is unlikely to risk devastation of a U.S. city to protect an Asian ally.

Of equal concern is that North Korea’s development of such an ICBM serves Beijing’s interests: It diverts U.S. resources; it gives China leverage in return for its cooperation on continued economic sanctions; and a North Korean, nuclear-tipped ICBM aimed at the U.S. has the prospect of reducing the credibility of U.S. promises to support its allies against North Korea.

It is not in Beijing’s present interests to place too much pressure on Mr. Kim’s regime. Thus, China’s strategy may be to cooperate enough with the United States to avoid undue U.S. pressure while buying time for North Korea to complete its development of a game-changing, operational, nuclear-armed ICBM.

Conversely, it is not in Beijing’s present interests to place too much pressure on Mr. Kim’s regime. The collapse of the North Korean regime risks the prospect of thousands of North Korean refugees crossing into China and of a unified democratic Korea on its border. This helps explain Beijing’s agreement in December to blacklist only four of the 10 cargo vessels that the United States identified as violating the UN sanctions: It does not want to cut off supplies to the point that it jeopardizes the regime’s stability. Thus, China’s strategy may be to cooperate enough with the United States to avoid undue U.S. pressure while buying time for North Korea to complete its development of a game-changing, operational, nuclear-armed ICBM.

Accordingly, we need an additional layer of strategy to accompany the sanctions—a strategy that changes China’s calculation of the costs and benefits of permitting the North Korean regime to continue to pursue its present course.

The announcement of a decision to install a perimeter of anti-missile defense systems around North Korea unless Pyongyang abandons its nuclear program might change China’s calculus of the risks associated with the North Korean program. Ironically, China revealed how a defensive perimeter could change its calculations when it reacted so harshly to South Korea’s announcement in July 2016 that it would deploy a Terminal High Altitude Area Defense (THAAD) system to defend against North Korean missiles.

China revealed that it views a defensive perimeter against Pyongyang’s missiles as a threat to its own strategic interests.

China viewed the radar associated with THAAD as undermining its own offensive missile capability against the United States. In response, China punished South Korea (for its audacity to defend itself) with severe economic sanctions and only lifted them when Seoul agreed not to install another anti-ballistic missile system or join a regional missile defense system or an alliance with the United States and Japan.

But in doing so, China revealed that it views a defensive perimeter against Pyongyang’s missiles as a threat to its own strategic interests. Thus, such a perimeter could change Beijing’s evaluation of the risks of North Korea’s continued development of nuclear weapons.

Recently, Japan announced that it was preparing to install anti-ship and anti-aircraft missile batteries at Ishigaki—one of its islands near the Senkaku Islands that are also claimed by China. Japan’s willingness to do this, despite the anticipated Chinese reaction, suggests that Japan may cooperate in establishing such a defensive perimeter to guard against the threat of North Korean missiles.

An announcement of a credible commitment to install such a defensive perimeter could immediately change Beijing’s calculus even before it is installed.

The announcement of our preparation of a defensive perimeter to protect against North Korean missiles—which could stretch from northern Japan to Guam (with or without South Korea’s participation if its agreement with China constrains it)—would have the following benefits:

First, the prospect of such a perimeter would alter China’s evaluation whether it is in its interest to take stronger Chinese action to halt the North Korean program.

Second, the beauty of a defensive perimeter is that, by definition, it is defensive. In 1861, President Lincoln had to decide whether to defend or merely resupply Fort Sumter, which the Confederacy had threatened in the prelude to the U.S. Civil War. Lincoln decided to put the Confederacy in the position of being the aggressor and only sent a flotilla to resupply the Fort. When the Confederates bombarded the Fort as the helpless flotilla watched, the South assumed responsibility for starting the Civil War—a fact Lincoln emphasized in his second inaugural address when he said, referring to the combatants, that one of the parties "would make war rather than let the nation survive; and the other would accept war rather than let it perish." A defensive perimeter places the United States on the high ground.

Third, an announcement of a credible commitment to install such a defensive perimeter could immediately change Beijing’s calculus even before it is installed. After all, President Reagan’s credible commitment to pursue the Strategic Defense Initiative was enough to alter Soviet behavior. And President Nixon’s ability to negotiate an antiballistic missile (ABM) treaty with the Soviet Union in 1972 was only made possible by Congress’s authorization in 1969 of an ABM system, which, by the way, passed by only one vote—the vice president’s.

If North Korea does develop a credible, nuclear-armed ICBM, the United States will need to have a credible anti-missile system in place in order to undermine North Korea’s retaliatory capacity.

Fourth, if China assists in "persuading" North Korea to abandon its nuclear program, and the United States thereafter agrees to halt installation of the defensive perimeter, this effort could launch arms control talks between Washington and Beijing. During the Cold War, such talks were exclusively between the United States and the Soviet Union. But such talks could play an important role in managing relations with a formidable rising power in the 21st century.

Finally, if North Korea does develop a credible, nuclear-armed ICBM, the United States will need to have a credible anti-missile system in place in order to undermine North Korea’s retaliatory capacity and to reduce its leverage in the event of a conflict. No purpose is served by waiting for the threat to materialize before preparing against it. Indeed, preparing against a threat is often the best way of avoiding it.

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Daniel Kolkey is a Pacific Council member and a former associate justice on the California Court of Appeal.

The views and opinions expressed here are those of the author and do not necessarily reflect the official policy or position of the Pacific Council.