Chinese President Xi Jinping leaves after a press conference [+] [-] at the BRICS Summit in Xiamen, Fujian province on September 5, 2017. Xi opened the annual summit of BRICS leaders that already has been upstaged by North Korea’s latest nuclear weapons provocation. (FRED DUFOUR/AFP/Getty Images)

The governments of South Korea and the United States expressed outrage at what appeared to be North Korea’s underground test of a nuclear weapon on Sunday. China condemned the test, too, after picking it up on seismic activity monitors. China has been North Korea’s immediate neighbor, economic benefactor and fellow Communist protector since the 1950s. Since the test of what North Korea describes as a hydrogen bomb that can be loaded into an intercontinental ballistic missile, China has shown signs of swinging toward a lot of other countries who worry about what the north is up to, including 21 missile tests to date this year.

China itself isn’t worried, though the test distracted attention from the buzz of its hosting the BRICS Summit for emerging economies. South Korea, because of its historic grievances with the north, is the most likely target of any test gone awry or a fit of anger by leader Kim Jong-un in Pyongyang.

But Beijing likes to use North Korea to cast itself as a sober, conciliatory world player rather than what other countries might otherwise allege: a mighty, unbending Communist state that throws its economy around to get what it wants abroad. What better way to make this point than to contrast itself to North Korea just after its sixth known nuclear test since 2006?

That psychology explains why China at least went along with Monday’s U.N. Security Council discussion where U.S. Ambassador Nikki Haley urged the severest possible sanctions against North Korea. Its lack of protest of the sanction idea goes with the Chinese foreign ministry’s Sunday comment that it would "unswervingly push forward the denuclearization of the peninsula," as quoted by the state-run China Daily news website.

"Beijing was unlikely to support additional U.N. sanctions that Washington, Seoul and Tokyo called for after North Korea’s August 29 intermediate-range ballistic missile test over Japan," says Leif-Eric Easley, assistant professor of international studies at Ewha University in Seoul. "However, a sixth nuclear test should unlock further Chinese cooperation on the Security Council."

China had acted as the bridge of cooperation between North Korea and its chief foes – Japan, South Korea and the United States – by hosting multilateral talks that were mothballed after five years in 2008. Its friendship with North Korea never fundamentally changed during those years. China still hopes to revive that dialogue.

But a Chinese consensus now with South Korea and the West on containing North Korea will probably last only until the Sunday blast has been forgotten – or put in perspective by a lesser test such as another missile launch. China may know its pressure doesn’t work to change North Korea itself. It also doesn’t want North Korea to fall, placing a war or humanitarian crisis at its doorstep and possibly bringing a Western ally – South Korea – closer depending on who took power in a weakened north. That’s why Beijing normally disapproves of strong sanctions. "I imagine there will be a resolution, but not necessarily any new sanctions," says Joshua Pollack, editor of the Nonproliferation Review in Washington.

Beijing’s Communist leaders are more likely over the next few weeks to talk North Korea out of new weapons tests while sustaining aid to keep Kim’s country stable. It may also point to South Korea and the United States as partially to blame for inflaming matters between the Koreas, leading to the suspected nuclear test.

"Beijing will continue to play both sides, meaning that they will blame both sides for the escalation," says Abraham Kim, a Korea analyst and executive-director at the Mike and Maureen Mansfield Center at the University of Montana. "On the one hand, Beijing will publicly be critical of North Korea and put pressure on Pyongyang to stop its march up the escalation ladder. On the other hand, their response will be carefully gauged to avoid a response that might trigger severe instability in North Korea, and possible collapse, and avoid the appearance that Beijing has completely abandoned North Korea."