On Feb. 8, the U.S. State Department released the latest in a series of acknowledgements that the United States and China agree that solving the problem of a nuclear-armed North Korea will take cooperation between the two nations. China has run hot and cold on North Korea before, but the current desire to rein in its rogue neighbor and sometime ally seems sincere. But a step that would truly demonstrate mutual resolve against the Kim regime’s pursuit of a nuclear arsenal is for the United States and China to cooperatively enforce sanctions against North Korea through a combined maritime interdiction operation.

In late 2017, the United Nations Security Council passed a series of increasingly harsh sanctions on North Korea in response to its recent missile and nuclear warhead tests. The sanctions are intended to seriously curtail North Korea’s trade, as well as targeting specific government entities and halting joint ventures with other countries. This is a strong message, but sanctions alone, which have been tried for decades, are not enough.

North Korean leader Kim Jong Un has often said he views these sanctions as primarily the work of the United States, a view reiterated in a statement by North Korea’s U.N. mission on Feb. 12. Convincing him that the time has come for him to reconsider his nuclear ambitions will require China’s active participation in sanctions enforcement. Such a move would convince North Korea that its sole ally and biggest trading partner had reached the end of its strategic patience.

But what could persuade China to cooperate with the United States like this? China has demonstrated extraordinary patience with North Korea, often in ways that seem to run counter to China’s long-term strategic goals. That now seems to be changing.

As China increasingly seeks to assert itself as a dominant player in the region, North Korea is becoming a liability. China still views North Korea as a strategic buffer against democratic South Korea and, by proxy, the United States, but the cost of propping up an embarrassing regime is outweighing the strategic value. What China seeks most of all is regional stability, and North Korea’s actions are having a markedly destabilizing effect on the Korean Peninsula.

North Korea’s actions have increasingly pricked China in sensitive spots. In May 2017, Kim chose to test a nuclear weapon just hours before President Xi Jinping was set to deliver a keynote speech on China’s increasing diplomatic influence. When North Korea directed its actions primarily at the United States, China was willing to tolerate them. Now that they have become an impediment to Xi’s domestic and diplomatic ambitions, that calculus has changed.

It is true, as many scholars have observed, that China will not intentionally allow the North Korean regime to collapse. China has a vested interest in preventing the potential flood of refugees streaming into its northeastern regions that might result from the sudden implosion of Kim’s regime — a nightmare scenario that is not in the United States’ interest, either. But there seems to be an increasing willingness to apply the screws to Kim over the nuclear issue.

That’s because Chinese leaders are beginning to understand that a nuclear-armed North Korea is a threat to their national interests as well. China’s ambassador to the United States, Cui Tiankai, has made clear that a nuclear-armed North Korea is as unacceptable to China as it is to the United States and the rest of the Asia-Pacific region. A nuclear-armed North Korea has the potential to spark a regional nuclear arms race that could spread to South Korea, Japan, and even Taiwan, whose own past nuclear program was curbed in 1988 under U.S. pressure. And while the possibility seems remote, North Korean nuclear weapons could aim at Chinese cities far more easily than American ones. Kim may one day find himself in need of a deterrent against Beijing if Xi’s government decides to act upon the growing belief in Chinese policy circles that Kim’s continued rule is detrimental to Chinese ambitions. Because it sees regional stability as the bedrock of continued economic growth, China cannot afford either a regional arms race or an unpredictable nuclear threat on its border.

As the pressure from sanctions mounts, Kim will likely seek alternative methods to maintain trade with the few nations willing to continue their illegal relationship with North Korea. Because it shares borders with only China and South Korea, North Korea will need to turn to the sea for what little trade it can muster. Maritime forces will be needed to interdict illicit shipping emanating from North Korea. The United States could conduct such an operation unilaterally or with close allies, but a joint effort with China would have a far greater impact.

Andrew Winner of the U.S. Naval War College recently argued that a U.S. interdiction effort to enforce the latest sanctions on the North Korea would have only a marginal impact in shaping Kim’s behavior. His assessment is correct if one views interdiction of maritime shipping solely as a means to an end. Decades of sanctions have forced North Korea to develop what John Park, director of the Harvard Kennedy School’s Korea Working Group, refers to as “sanctions immunity,” in essence a resiliency developed in response to decades of sanctions that enables North Korea to withstand their most debilitating effects. There is little, short of completely cutting off North Korea from the outside world, that would drive major changes in Kim’s calculus.

But it isn’t the sanctions themselves that really matter in this case, it is who is enforcing them. If the United States attempts to enforce sanctions alone or only with close allies, the latest round of sanctions is unlikely to deter North Korea. Chinese participation and joint enforcement, however, would send Kim the message he needs to hear.

The U.S. Navy and Chinese People’s Liberation Army Navy operate in the region every day. The United States has warships based in Japan and Singapore that can quickly reach the coast of North Korea and can operate there nearly indefinitely. Although the Chinese navy currently lacks the U.S. Navy’s robust ability to sustain itself at sea, the proximity of Chinese naval bases to North Korean waters would eliminate China’s need for a logistics infrastructure on the scale that the U.S. Navy possesses.

Trust between the United States, China, and their respective navies is often strained, but there is a precedent for cooperation. Joint operations with foreign naval forces are a hallmark of the U.S. Navy. Although China is a relative newcomer to multinational naval operations, it has demonstrated the ability to successfully work with other navies. The Chinese navy has already participated in operations and exercises with international partners, including anti-piracy efforts off the coast of Somalia and Rim of the Pacific Exercises in 2014 and 2016, during which it participated with the U.S. Navy in counterpiracy and maritime security exercises — exactly the skills needed for maritime sanctions enforcement. These events demonstrated that the U.S. and Chinese navies can operate safely in close proximity with one another. It’s true that those exercises were scripted and predictable, so miscommunications or misunderstandings were avoided through careful planning. But it was also a useful preparation for real-world operations.

U.S. Navy and Chinese navy ships already operate near one another and communicate with one another frequently and professionally, even during controversial missions such as freedom of navigation operations. It is true that episodes have occurred in which Chinese units have acted unsafely while attempting to dissuade the United States from challenging excessive Chinese territorial claims. Such incidents are, however, unusual and not in keeping with the “normal safe behavior” of the Chinese military. Despite underlying political tensions between the United States and China, the crews that man the ships of these two navies deal with each other as professional mariners and have protocols in place to diminish the risk of a misunderstanding leading to unintended conflict.

Previous experience can provide a workable model for future cooperation, starting with relatively simple efforts such as direct lines of communication, and working up to more complicated operations that might, for instance, require close coordination or even temporarily place U.S. and Chinese ships under the direction of the other side. While there would no doubt be friction, the long-term effect would be to ease tensions and alleviate discomfort and suspicion. That could carry over even into other theaters where U.S. and Chinese interests differ radically, such as the South China Sea.

A combined U.S.-Chinese naval operation to enforce sanctions against North Korea would be less about interdiction and more about messaging. The North Korean regime has survived and continued its march toward nuclear armament in no small part due to the protection afforded by China. China’s participation in sanctions operations with the United States would send a clear message that it is time for Kim to reconsider North Korea’s strategic options if he wants to remain in charge.

In his recent 38 North article, Winner, the Naval War College professor, argued that the benefits associated with conducting interdiction operations against North Korean ships are outweighed by the risks of North Korean escalation, up to and including war. While Kim might just be reckless enough to attack a U.S. warship operating alone, it is hard to believe he would risk attacking his only benefactor, China, or those working closely with it. Bringing China into the exercise would thus significantly diminish the risk of conflict, not exacerbate it.

Finally, Chinese participation with the United States in maritime sanctions enforcement would lend it undeniable international legitimacy. While Kim might be able to convincingly argue that previous sanctions enforcement efforts were the work of a U.S. government hostile to his regime, such an argument would lose all credibility if both the United States and China were active participants.

Decades of sanctions against the North Korean regime have proved largely ineffective, primarily because North Korea could always rely on China to insulate it from the worst consequences of those sanctions. There is no reason to believe that the newest round of sanctions, if enforced solely by the United States and its allies, would be effective. It is time to change Kim’s strategic calculus. A combined U.S.-Chinese maritime sanctions enforcement operation is a good place to start.