When US President Barack Obama and Chinese President Xi Jinping met for their “shirt-sleeves summit” in California last month, North Korea was a major topic of conversation. The subject was not new, but the tone was.

More than two decades ago, the International Atomic Energy Agency caught North Korea violating its safeguards agreement and reprocessing plutonium. After the North renounced the subsequent Agreed Framework, negotiated by President Bill Clinton’s administration, in 2003, it expelled IAEA inspectors, withdrew from the Nuclear Non-Proliferation Treaty, and has since detonated three nuclear devices and conducted a variety of missile tests.

During those two decades, American and Chinese officials frequently discussed North Korea’s behavior, both privately and in public meetings. The Chinese consistently said that they did not want North Korea to develop nuclear weapons, but claimed that they had limited influence over the regime, despite being its major supplier of food and fuel. The result was a somewhat scripted exchange in which China and the US would accomplish little more than professing denuclearization as a shared goal.

China was sincere in expressing its desire for a non-nuclear Korean Peninsula, but the nuclear issue was not its primary concern. It also sought to prevent the collapse of the North Korean regime and the resulting potential for chaos on its border – not only flows of refugees, but also the possibility that South Korean or US troops could move into the North.

Torn between its two objectives, China placed a higher priority on preserving the Kim family dynasty. That choice gave rise to a seeming paradox: North Korea gained surprisingly powerful influence over China.

North Korea has what I call “the power of weakness.” In certain bargaining situations, weakness and the threat of collapse can be a source of power. To take a well-known example, if you owe a bank $1,000, the bank has power over you; but if you owe the bank $1 billion, you may have considerable bargaining power over the bank. China is, in this sense, North Korea’s over-exposed banker.

As a result, China has tried to persuade North Korea to follow its market-oriented example. But, with the Kim regime terrified that economic liberalization would eventually provoke demands for greater political freedom, China’s influence over the regime is limited. As a Chinese official once told me in an unguarded moment, “North Korea has hijacked our foreign policy.”

North Korea has amplified its power by playing its weak hand audaciously. The North’s leaders know that superior South Korean and US military forces would win a full-scale military conflict. And yet, with 15,000 artillery tubes in the Demilitarized Zone, just 30 miles (48 kilometers) north of Seoul, the South Korean capital, they also know that they could wreak havoc on South Korea’s economy, whereas the North has relatively less to lose.

North Korea has long been adept at flaunting its willingness to take risks, provoking a crisis in 2010 by sinking a South Korean naval vessel and shelling a South Korean island. This spring, it conducted a nuclear test and a series of missile tests, accompanied by a stream of bellicose rhetoric.

Now it appears that China is beginning to lose patience. It has less confidence in the North’s inexperienced new ruler, Kim Jong-un, than it had in his father, Kim Jong-il. Chinese leaders are also beginning to recognize the risks that North Korea is imposing on China.

With more nuclear tests, a demand for nuclear weapons could grow in South Korea and Japan. Moreover, if this spring’s sharp rhetoric from the Kim regime is followed by provocations against South Korea like those that occurred in 2010, South Korea could respond forcefully, and China might be drawn in.

The signs of a change are intriguing. Following the “frank” discussion of North Korea by Xi and Obama, Xi hosted a summit with South Korean President Park Geun-hye, without first meeting with its official North Korean ally. Instead, two senior North Korean officials subsequently visited Beijing and were scolded for the North’s behavior.

By contrast, Xi and Park issued a joint statement proclaiming the importance of faithfully implementing United Nations Security Council resolutions that call for sanctions against North Korea, as well as a multilateral agreement in 2005 that obliges the North to exchange its nuclear-weapons programs for economic and diplomatic benefits. Both leaders urged a resumption of the six-party talks on denuclearization, which have been suspended since 2009.

What comes next is uncertain. North Korea has tempered its rhetoric and behavior, but the Kim regime has given no indication that it is willing to give up the nuclear-weapons program that it regards as vital to its security and prestige. In the long run, economic and social change may help to resolve the situation. China’s dilemma remains that if it pushes too fast for reform, the Kim regime may collapse.

Faced with that prospect, the US and South Korea could take steps to reassure China that they would not exploit such a situation by moving their troops to China’s border. In the past, when the US has suggested quiet talks to discuss contingency planning in the case of regime collapse, China has been wary of offending and weakening North Korea. But finding a formula to talk about such contingencies may be the next step for China as it seeks to overcome its quandary.

The opinions expressed here are those of the author, not necessarily those of the World Economic Forum. Published in collaboration with Project Syndicate.

Author: Joseph S. Nye is a professor at Harvard University and the author of Presidential Leadership and the Creation of the American Era.

Image: Two soldiers from North Korea stand guard behind the flags of China and North Korea REUTERS/Jacky Chen