HONG KONG — North Korea's nuclear test is a rebuff of China's bid to rein in its uncooperative ally at a time President Xi Jinping is seeking to display his diplomatic prowess on the world stage.
North Korea said it tested a hydrogen device Wednesday, the second nuclear detonation since Xi became China's leader in late 2012. China wasn't informed in advance of the test and is "steadfast in its position that the Korean Peninsula should be denuclearized," Foreign Ministry spokeswoman Hua Chunying said in Beijing.
China has long touted its economic and diplomatic sway over North Korea. But relations soured after Kim Jong Un succeeded his father Kim Jong Il, who had bolstered economic ties between the communist regimes through regular meetings with Chinese leaders and visits to the country.
In his four years in power, the younger Kim has veered from that model: He's yet to sit down with Xi and has snubbed efforts to restart China-backed disarmament talks. He even executed his pro-Beijing uncle to tighten his grip on power.
"Xi has got to be fuming," said Clay Chandler, managing director of Barrenrock Group, a Hong Kong-based risk consultancy. "This runs counter to all of China's foreign policy objectives, and makes mighty China seem weak - incapable of restraining even a small impoverished neighbor that is almost totally dependent on China for economic survival."
China's Communist Party has been the North Korean regime's main economic and political benefactor since the early days of the Cold War, with the two sides teaming up against U.S. and South Korean forces during the 1950-53 civil war on the peninsula. China accounted for 79 percent of North Korea's trade in 2014, the most recent year available, up from 56 percent in 2010.
While North Korea's economic dependence on China has increased, the nuclear test is likely to mark a deterioration in diplomatic relations. Ties suffered after Kim executed his uncle, Jang Song Thaek, who had promoted commercial links with China, in December 2013. Kim provoked China's ire in February of that year by conducting a third nuclear test, prompting China to back U.S.-led efforts for more United Nations sanctions against the regime.
Signs of the strain were apparent when Xi made his first official visit to the Korean peninsula a trip to Seoul to meet Kim's nemesis, President Park Geun-hye, in July 2014. Xi has also hosted Park for a summit in Beijing.
Relations have see-sawed. Xi sent a high-ranking envoy to Pyongyang in October to a military parade carrying a handwritten letter seeking deeper cooperation.
Last month, signs of tensions resurfaced. Two days after Kim declared that North Korea had developed a hydrogen bomb, a rare concert in Beijing by a North Korean all-girl pop band was abruptly canceled. The group returned to Pyongyang after refusing demands by Chinese authorities to remove images of North Korean missile launches from videos to be projected during their performance, South Korea's Chosun Ilbo newspaper reported.
The U.N. Security Council is set to meet Wednesday, Reuters reported, with China expected to back new sanctions against Pyongyang. Still, it may be reluctant to dole out too much in the way of bilateral punishment for fear of destabilizing the regime.
Political unrest could trigger a flood of refugees across their 880-mile shared border, and any collapse could lead to reunification with South Korea, raising the possibility of a U.S. ally sitting on China's frontier.
China still has some pull with North Korea but is worried about using it, Council on Foreign Relations President Richard Haass said on Bloomberg Television. "I would argue that the real goal for American foreign policy is to bring about a sea change in Chinese thinking," he said. "That it's riskier to tolerate a nuclear North Korea than it would be to put pressure on a nuclear North Korea."
While the test may lead to more China-U.S. cooperation at the UN to contain North Korea, it risks sparking tensions between the two powers in Asia, should the U.S. seek to place a missile defense system in South Korea to counter North Korea's improving weaponry.
China has already warned South Korea against considering pursuing deployment of the Terminal High Altitude Area Defense anti-ballistic missile system. Lawmakers from Park's ruling party have been lobbying to obtain the system to counter the nuclear threat from the North.
"All eyes will be on China to see whether this fourth nuclear test near its border will finally compel a change in Beijing's support of the regime, " Victor Cha, a senior adviser at risk consultancy Teneo Intelligence in Washington, DC, said by email. "Beijing is likely to support a UN Security Council resolution as well as making some tactical adjustments to its flow of assistance to the Pyongyang government in the short- term, but at present there is no indication of a longer-term strategic change in Chinese support for North Korea."
North Korea claimed Wednesday to have successfully detonated a hydrogen bomb, a device potentially hundreds of times more powerful than the atomic bombs of its previous tests. That claim drew immediate skepticism from weapons experts as only seven nations are known to have tested hydrogen weapons, including the U.S. and China, according to the Stockholm International Peace Research Institute. Still, the boasts reflect Kim's goal to develop the more powerful weapons.
"The test shows China keeps losing control of North Korea issues," said Shi Yuanhua, director of the Center for Korean Studies at Fudan University in Shanghai. "The relationship between the two countries is damaged and will take a long time to heal."
Ting Shi, Clement Tan, Keith Zhai and Patrick Donahue contributed.