BEIJING, September 3 (Reuters) - North Korea's latest nuclear test is likely to pile more pressure on China to take tough action against its neighbour, but Beijing already doubts economic sanctions will work and says it is not its sole responsibility to rein in Pyongyang. China has lambasted the West and its allies over recent weeks for promoting the "China responsibility theory" for North Korea, and been upset by Seoul and Washington's own military drills that Beijing says have done nothing to cool tensions. "The United States has to play its own role and should not be blindly putting pressure on China to try and squeeze North Korea," said Ruan Zongze, a former Chinese diplomat now with the China Institute of International Studies, a think-tank affiliated with the Foreign Ministry. While the seriousness of Sunday's nuclear test means China will likely support tough new action, including possibly cutting off oil supplies, China will make clear others need to step up too, Ruan added. Over the past week, China's foreign ministry has repeatedly hit back at calls from Western countries and Japan for China for to do more to rein in North Korea, saying that pushing for dialogue was an equally integral part of the U.N. resolutions, and that escalating sanctions alone had been evidently ineffective. "On the one hand, sanctions have continued to be put in place via resolutions and on the other hand North Korea's nuclear and missile launch process is still continuing," ministry spokeswoman Hua Chunying said last week. The Global Times, a state-run newspaper, also attacked British and Australian leaders for calling on China to do more, especially Australian Prime Minister Malcolm Turnbull's suggestion that China should cut off oil supplies to North Korea. The tone in which China has pushed back has had some Western diplomats raising questions over the extent to which Beijing would be willing to stomach further sanctions, before it argues that they could destabilise the Kim Jong Un regime. China's big fear has always been that cutting North Korea off completely could lead to its collapse, unleashing a wave of refugees into China's rustbelt provinces in the northeast. One Beijing-based Western diplomat, speaking late last week before the nuclear test, said China had cooperated with the United States on sanctions to a certain degree, in order not to give Washington a pretext for a military strike. "But they won't go far enough to have an impact on North Korea's determination to become a nuclear power," the diplomat said, speaking on condition of anonymity. "WRONG ACTIONS" China has not publicly said it will back new sanctions. A brief Foreign Ministry statement on Sunday condemned the test and urged North Korea to stop its "wrong actions" and return to talks. Zhang Liangui, a North Korea expert at the Central Party School, which trains rising officials, however said Pyongyang had made repeatedly clear that it would not give up its nuclear weapons programme and that while sanctions were unlikely to prove useful, the chances of resolving the Korean peninsula crisis through talks were also "miniscule, if not already non-existent". The Global Times, published by the ruling Communist Party's official People's Daily, wrote in April that Chinese people would approve of far tougher action, including restricting oil exports, if North Korean provocations continued. China, which supplies most of North Korea's crude, no longer reports its oil shipments to the country, but according to South Korean data supplies it with roughly 500,000 tonnes of crude oil annually. It also exports over 200,000 tonnes of oil products, according to U.N. data. The timing of the nuclear test overshadowed the start of a summit of the BRICS group of nations in the southeastern Chinese city of Xiamen, coming just hours ahead of a keynote speech by President Xi Jinping. Xi himself did not mention North Korea during a 45-minute speech, while Chinese state media gave top billing to him and the summit, with the nuclear test receiving only passing mention. To be sure, China has a lot to gain by stopping North Korea's nuclear and missile tests, and China says it is committed to the U.N. sanctions already in force. North Korea is an unpopular country with ordinary Chinese, though there is still a residual feeling of loyalty to Pyongyang in the military owing to shared sacrifices in the 1950-53 Korean War, diplomats and sources with ties to the military say. Ruan, the former diplomat, said quick action was needed to address the problem as both North Korea and the United States were stepping up their war of words and appeared to be goading each other towards armed conflict. "You certainly can't rule out the possibility that weapons will be used," he said.