Last weekend’s summit between U.S. President Barack Obama and Chinese counterpart Xi Jinping marked the start of a process toward forming what will amount to a new world order. Over the course of two days in the informal setting of a sprawling California desert estate designed to encourage free-flowing discussion, the two leaders agreed to build a “new type of great power relationship” between their countries.

What emerged as a conspicuous area for cooperation in the envisioned relationship was to denuclearize North Korea. Briefing the results of their talks, U.S. National Security Adviser Tom Donilon said they reached a “full agreement” that the North had to be denuclearized and that neither country would accept it as a nuclear-armed state. The two leaders achieved “quite a bit of alignment” on the issue, Donilon said, praising recent steps taken by Beijing to enhance enforcement of sanctions against Pyongyang for provocative acts including its third nuclear test in February. In a separate briefing after the summit, Chinese State Councilor Yang Jiechi said Xi had told Obama that the two sides were “the same in their positions and objectives” on the North Korean nuclear issue.

China’s explicit message of cooperation with the U.S. on denuclearizing North Korea will force the recalcitrant regime in Pyongyang to decide whether to continue to push for its nuclear weapons program at the risk of losing support from its only remaining major ally. As noted by some experts here, it may have yet to be seen how far China will go in putting pressure on its impoverished neighbor. But it seems that China has taken the course of joining forces with the U.S. to denuclearize the North as a key element of its grand diplomatic strategy of forming a new type of great power relationship to seek win-win cooperation, rather than confrontation. China’s shift in policy was also apparently prompted by its concern over a possible nuclear domino effect in other regional countries.

Many observers here interpreted North Korea’s sudden proposal for government-level talks with South Korea last week as a move designed to strengthen the Chinese leader’s hand in his summit with Obama. But it was more likely to be an attempt to shield itself from change in Beijing’s stance. The outcome of the Obama-Xi meeting was briefed hours before South and North Korea began working-level contact at the truce village of Panmunjeom on Sunday to set up a high-level government meeting scheduled for Wednesday in Seoul. It would have been more embarrassing for Pyongyang to propose talks with Seoul after U.S. and Chinese leaders demonstrated a concerted stance on its denuclearization.

Pyongyang may try to deflect the pressure by putting forward ambiguous preconditions for dismantling its nuclear armament. Despite their “absolute agreement” to denuclearize the North, the U.S. and China have yet to draw up a specific road map for achieving that goal.

In this context, South Korea should assume a more active role in working out measures instrumental in denuclearizing North Korea. It needs to strengthen tripartite coordination with Washington and Beijing, while taking a principled and flexible position in the upcoming inter-Korean talks, which will serve to gauge whether Pyongyang will discard its nuclear program and for what conditions. South Korean President Park Geun-hye’s trip to China late this month should be another occasion to drive home to North Korea the message that its dual goals of developing its economy while expanding its nuclear arsenal will take it nowhere.