Beijing: North Korea's sixth nuclear test was expected. The timing speaks of Kim Jong-un's willingness to provoke China; and an attempt to seize the moment to wedge South Korea and Donald Trump.
A military response from the United States appears less likely than a decision by China to finally reach for its biggest gun - cutting the oil pipeline to North Korea.
More World News Videos
Will Trump attack North Korea?
As North Korea conducts its sixth and most powerful nuclear test, US President Trump considers his response.
North Korea, for its part, thinks it has just strengthened its hand for talks.
The United States has been urging China to cripple North Korea by cutting its energy supply. China has to date resisted and Chinese foreign policy analysts have said this is because Beijing had to keep one card up its sleeve for the day Pyongyang crossed its red line.
China hates nuclear tests on its border the way the US hates an intercontinental ballistic missile test that could potentially reach the US mainland.
The two North Korean earthquakes, measured by Chinese monitors as magnitude 6.3, and then magnitude 4.6, triggered by the hydrogen bomb explosion on Sunday, prompted reports of tremors in Chinese border towns and scrambled Chinese jets. As with the five earlier nuclear tests, there is fear of radiation leaks.
Renmin University's professor of international relations, Shi Yinhong, had warned earlier in the week that China was in a difficult diplomatic situation - North Korea was acting increasingly hatefully towards China as it toughened economic sanctions.
The timing of Sunday's nuclear test indeed appears an act of spite against Beijing.
![North Korea's state media said leader Kim Jong Un inspected the loading of a hydrogen bomb into a new intercontinental ...](http://web.archive.org./web/20170906070924im_/https://www.fairfaxstatic.com.au/content/dam/images/g/y/9/n/y/d/image.related.articleLeadwide.620x349.gy9sva.png/1504469621923.jpg)
North Korea's sixth nuclear test was conducted as leaders from Russia, Brazil, India, and South Africa flew into China for the much-heralded BRICS summit of emerging economies, at which Chinese President Xi Jinping was due to give a speech.
It is the second time this year North Korea has spectacularly disrupted Beijing's attempt to highlight its place on the world stage. Xi's One Belt One Road forum, with 30 world leaders in attendance, was punctuated by a North Korean missile test.
![Chinese President Xi Jinping with Brazil's President Michel Temer, right, in Beijing on Friday.](http://web.archive.org./web/20170906070924im_/https://www.fairfaxstatic.com.au/content/dam/images/g/y/9/w/o/o/image.related.articleLeadwide.620x349.gy9sva.png/1504468532455.jpg)
But the timing of Sunday's hydrogen bomb test also exploits tension between South Korea and the United States. On Saturday, South Korean foreign policy analysts were stunned that US President Trump - in his latest act of trade brinksmanship messing with security interests - threatened to axe a trade pact with South Korea as soon as this week.
On Friday, ahead of BRICS, Russian President Vladimir Putin described US tactics on North Korea as "misguided and futile", and said there must be dialogue between the US, South Korea and North Korea with no preconditions.
![China needs to believe that a unilateral US strike is a credible prospect.](http://web.archive.org./web/20170906070924im_/https://www.fairfaxstatic.com.au/content/dam/images/g/y/9/n/y/l/image.related.articleLeadwide.620x349.gy9sva.png/1504623423190.jpg)
Russia believes North Korea will not give up its nukes.
South Korea, under new president Moon Jae-in, has said it is open to talks with its neighbour, but has so far toed the US line by repeating the caveat that preconditions must be met.
![People in Seoul watch a TV news report about a possible nuclear test conducted by North Korea.](http://web.archive.org./web/20170906070924im_/https://www.fairfaxstatic.com.au/content/dam/images/g/y/9/t/e/d/image.related.articleLeadwide.620x349.gy9sva.png/1504468532455.jpg)
US Secretary of State Rex Tillerson has articulated US preconditions for talks with North Korea as no more missile tests and an agenda focused on North Korean denuclearisation.
But the rapid progress of North Korea's missile technology, its attainment of an intercontinental ballistic missile, and the latest nuclear test now have many analysts saying negotiations may need to begin with an acceptance of North Korea as a nuclear state.
"There is no strike option that is not a war. We are beyond 'prevention' and there is a third option: diplomacy and negotiation," wrote Professor John Delury of Yonsei University in Seoul.
China has said it wants denuclearisation but has grown increasingly irate at the US in the past fortnight, after Washington imposed unilateral sanctions on Chinese companies caught dealing with North Korea.
China's spokeswoman snapped that some parties appeared disinterested in peace talks and dialogue, only threats.
China's foreign ministry went so far as to blame the US and South Korea for conducting a large, week-long military drill that has historically provoked Kim. North Korea's fifth nuclear test, in 2016, was also conducted soon after the joint US military drill that North Korea has strongly protested is a threat to its security.
If the ball is in China's court on cutting oil, it may demand more willingness from the US to come to the negotiating table with North Korea.
Pyongyang, anticipating oil sanctions, has reportedly been stockpiling fuel for months.
North Korea on Sunday declared the test had confirmed it now has a hydrogen bomb capable of fitting on an intercontintental ballistic missile, and so the "DPRK-US confrontation structure has fundamentally changed".