Hong Kong ( CNN ) -- The naughty step is not working . After the United Nations slapped tougher sanctions on North Korea after its third nuclear test in February this year , Pyongyang screamed in defiance . It canceled its hotline with South Korea , withdrew its workers from the Kaesong industrial complex it jointly operates with Seoul , and carried on with its over-the-top threats . China may have backed those sanctions but the economic lifeline is still there . Trade goes on between North Korea and China . In 2011 , before some of these trade embargoes began , China accounted for an estimated 67.2 % of North Korea 's exports and 61.6 % of imports , according to the CIA World Factbook . `` If you talk to officials at the border , there 's no change , '' says Stephanie Kleine-Ahlbrandt , the North Asian head of the International Crisis Group . `` And a lot of that trade is conducted by government trading companies especially on the North Korean side , '' adds the Los Angeles Times ' Beijing Bureau Chief Barbara Demick . `` There 's a lot more China could do that it has chosen not to . '' So why is China not using its economic leverage to rein in the nuclear threat and proliferator next door ? In a word -- fear . There 's fear of a North Korean collapse that would lead to instability and a refugee crisis along its 1,400 kilometer ( 880 mile ) border with North Korea . And then there 's the far greater fear of an all-out conflict that would redraw the geopolitical map . `` Their end goal might be similar in terms of denuclearization , but China is looking at preventing war on the peninsula , which would allow a pro-Western government right on its border , '' says Kleine-Ahlbrandt . And there 's something else holding Beijing back -- the historic and symbolic relationship with Pyongyang that is hard to give up . `` The Chinese Communist Party thinks of North Korea as this small state that is in its own image , '' says Demick . `` The structure of the North Korean government is very similar to the Chinese government and , in a way , it 's the pure Communist state . `` It 's just really hard psychologically to dump North Korea . '' `` They treat North Korea a bit like a wayward child , '' adds Kleine-Ahlbrandt. `` You want to be the one to punish your child , but you 're not going to turn them over to police . '' But for many people in China , enough is enough . `` Their rhetoric is increasing the number of Chinese who feel very , very disgusted by their behavior , their psyche and their regime , '' says Zhu Feng , professor of International Relations at Peking University . `` China 's government is seriously under fire because I think the majority of Chinese really , really feel that North Korea 's bad behavior will inevitably endanger China . '' Beijing has mastered the art of `` scream-free parenting '' with Pyongyang . It has learned to lower its voice and control its emotional reaction with every new threat or missile test . But public opinion is shifting and China 's new leadership is recognizing the need to re-evaluate how it manages its troublesome neighbor . In a sign of Beijing 's evolving approach toward North Korea , Chinese President Xi Jinping recently offered this veiled criticism : `` No one should be allowed to throw a region and even the whole world into chaos for selfish gains . '' The pressure is on for China to spell out -- and carry out -- the consequences for North Korea 's bad behavior .
Pyongyang reacted angrily to tougher sanctions after its third nuclear test . The United States and South Korea have been pushing for a new round of U.N. Security Council sanctions. But Beijing has struggled to control the angry rhetoric from its neighbor . Expert : China fears a North Korean collapse would spark a refugee crisis .