North Korea's surprise claim that it had successfully conducted a fourth nuclear bomb test this week renewed fears and ignited a chorus of condemnation around the world.
If confirmed, the detonation would be the first to use fusion technology - a major step up in North Korea's nuclear weapons capability.
South Korea and Japan had swiftly threatened increased sanctions, and pledged with the US to forge a "united and strong" international response. The United Nations Security Council also agreed to draw up new measures against North Korea.
The isolated communist regime's most important economic ally, however, has so far only called on Pyongyang to return to the negotiating table and to give up its nuclear weapons.
On Wednesday, China's foreign ministry released a statement saying it "firmly opposes" the test, and a spokeswoman told reporters that Beijing would be summoning Pyongyang's ambassador to lodge a complaint.
This is not the first time China has disappointed international leaders with a weak response to its neighbour's hydrogen bomb testing.
Pyongyang tested its first nuclear device 10 years ago, contravening Security Countil resolutions and leading to the imposition of economic sanctions by the UN.
China did not use its veto power on the UN Security Council to block such sanctions, but its government has also not answered calls to leverage its power to put stronger pressure on North Korea.
In 2013, Beijing cut crude oil exports to North Korea following the country's previous nuclear test but stopped short of cutting ties that would have seriously affected the country's economy.
"There is no doubt that China is a kind of lifeline for North Korea," said Eric Ballbach, an expert on North Korea at Berlin's Freie Universität. "But China has not been willing to use this economic influence with full force and this has not changed even after the most recent test."
China's foreign ministry confirmed Wednesday it had not received advanced warning that North Korea would be conducting the nuclear test.
While this was a "clear snub" to the Chinese leadership, Beijing may still only pursue "subtle coercive measures" such as the temporary restriction of economic cooperation pilot projects, said Mikko Huotari of the Mercator Institute for China Studies.
"China's strategy continues to be characterized by the following priorities: No war, no instability, no nuclear weapons," Huotari said.
China is treading carefully because it is afraid the Kim Jong-un leadership will collapse if there is too much pressure on the regime's economy. This could potentially lead to a flood of North Korean refugees into China, experts said.
"The worry is always there for China. They will not cut military support and investment in North Korea even if they are willing to make some economic sanctions," said Yu Yingli, associate researcher at the Shanghai Institutes for International Studies.
International observers could also be overestimating China's friendship with North Korea.
China's president Xi Jinping and Kim Jong-un have never met and Chinese state media have increasingly published scathing criticism of the regime.
"China has cleaned up the DPRK's [Democratic People's Republic of Korea's] mess too many times... But it doesn't have to do that in the future," retired Chinese general Wang Hongguang wrote in the state-run Global Times in 2014.
Wang's commentary also accused North Korea of violating the spirit of the two countries' mutual defense treaty by failing to consult China on its nuclear programme.
However, following a long frosty period between the countries, the Chinese leadership sent a politburo member to a military parade in October to mark 70 years since the founding of the Workers' Party of North Korea, suggesting a thaw in relations.
"China and the international community have to work to find an effective strategy because North Korea is not listening to anyone," said Zhang Liangui, a professor at the the Institute for International Strategic Studies of the Central Party School of the Communist Party of China.
"Pushing for sanctions is still important. If there were no sanctions at all, North Korea's nuclear weapon's development would be even faster. Sanctions might not eliminate the threat, but it may help to slow their weapons development," said Shi Yinhong, international relations professor at the People's University in Beijing.
Wednesday, January 27, 2016 - 08:36
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