Beijing (CNN) China -- North Korea's only global ally and biggest trading partner -- has put on a stoic face since Pyongyang successfully conducted its sixth nuclear test Sunday.

President Xi Jinping didn't mention his country's unruly neighbor at all in his closing address at the BRICS summit of emerging economies Tuesday, or in earlier speeches, although a communique issued by the group expressed deep concern and called for the crisis to be settled peacefully.

But the test of a hydrogen bomb couldn't have sat well with China's leader.

It's the third time in one year that North Korea has overshadowed a major Chinese event -- previous missile tests coincided with the unveiling of Xi's global economic blueprint at his Belt and Road summit in May and the G20, which China hosted last September.

"The Chinese have been pressing North Korea very hard not to stage a nuclear test," said Mike Chinoy, a former CNN Beijing bureau chief and the author of "Meltdown: Inside the story of the North Korean Nuclear Crisis."

"For the North Koreans to deliberately choose a few hours before a very important summit meeting when Xi Jinping is hosting the leaders from India, Brazil and South Africa -- a big, big deal for the Chinese -- is a deliberate poke in the eye from North Korea."

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Policy challenge?

The Chinese foreign ministry quickly and dutifully condemned the test, its statements sticking to the usual talking points of Beijing's commitment to a nuclear-free Korean Peninsula and resolving the issue through peace talks.

In academic circles and on social media, however, Chinese voices started to deviate from the official line -- noting the deliberate timing and challenging long-held notions that have formed the foundation of China's North Korea policy.

"The US, China and the rest of the world are facing a critical choice: Do we still insist on the denuclearization of the peninsula or do we accept its failure and recognize North Korea as a nuclear power?" said Zhang Liangui, a professor of international strategy at the ruling Communists' Central Party School and an expert on North Korea.

"It's not that United Nations sanctions don't work -- it's that the sanctions aren't tough enough," he said.

"If the precondition for such sanctions is that they can't destabilize North Korea politically, then the sanctions are bound to be useless. If you are not making the leader's life difficult, of course they won't change their policy."

Zhang's point appears to stand in sharp contrast to those expressed by Beijing officials, who have repeatedly said sanctions alone won't work, calling for negotiation, and rejected any punitive measures outside the UN framework.

China and Russia have called on the US and South Korea to suspend military drills in exchange for Pyongyang's halt of its nuclear weapons development, a proposal US Ambassador to the United Nations Nikki Haley slammed as China and Russia have called on the US and South Korea to suspend military drills in exchange for Pyongyang's halt of its nuclear weapons development, a proposal US Ambassador to the United Nations Nikki Haley slammed as "insulting."

"When a rogue regime has a nuclear weapon and an ICBM pointed at you, you do not take steps to lower your guard. No one would do that. We certainly won't," she said Monday.

Zhang says the UN's inability to exert any influence over North Korea called its role into question.

"Faced with such a serious issue with the entire non-proliferation system in danger and a potential nuclear war on the horizon, all the major powers seem powerless -- that's a tragedy," Zhang said.

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'Outdated' view

Many Western analysts believe that while Beijing is frustrated with North Korea, it prefers a nuclear-armed Pyongyang for two reasons.

It fears the collapse of the regime could lead to a refugee crisis on its doorstep and, more importantly, it believes that North Korea acts as a strategic buffer between China and South Korea, where the US maintains a large military presence.

However, Li Fang, a current affairs commentator, said on WeChat, a popular social media platform, that viewing North Korea as a buffer state was "outdated."

"Even if China and the US go to war, the US wouldn't send its troops across the Yalu River (along the Chinese-North Korean border) -- it would simply launch missiles from locations out of the Chinese army's reach. It's almost meaningless to treat North Korea as a strategic buffer."

"On the contrary, if North Korea thinks that China treats it as a buffer state, it would consider itself invaluable and wouldn't really cooperate."

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Both analysts pointed to the increasing inevitability of accepting North Korea as a nuclear power.

"If we can't stop this prospect, then we should use it as an opportunity to rid ourselves of historical burdens as well as useless sentiment and fantasies," Li wrote. "We can start treating North Korea as an equal and normal country -- and that's what (North Korean leader) Kim Jong Un wants anyway."

Relations between Pyongyang and Beijing have been frosty since Kim succeeded his late father as dictator, promptly purging several key government figures with strong ties to China, including his uncle Jang Song Thaek who was executed.

The murder in Malaysia of Kim's older half brother, Kim Jong Nam, who was living in the Chinese territory of Macau, is likely to have further soured ties.

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China 'won't solve' North Korea for Trump

While more voices are diverging from Beijing's official position, nobody seems to be suggesting that China is willing or able to bring more pressure to bear on its neighbor -- something US President Donald Trump has long insisted could fix the North Korea problem.

After Pyongyang's latest nuclear test, Trump tweeted that "North Korea is a rogue nation which has become a great threat and embarrassment to China, which is trying to help but with little success."

..North Korea is a rogue nation which has become a great threat and embarrassment to China, which is trying to help but with little success. — Donald J. Trump (@realDonaldTrump) September 3, 2017

"The US, as a superpower, has the means to resolve the issue," said Zhang, predicting the rising possibility of American military actions against North Korea under Trump. "It depends on the US' strategic determination and sense of responsibility."

"But if it hopes to see China resolve the issue, it simply won't work," he added.

"Many Chinese are supportive of North Korea's nuclear weapons program, thinking it is targeting the US and not a threat to China, while others think China's effort to denuclearize North Korea would only help the US."