CHINA responded with rare fury to neighbouring North Korea’s nuclear test, resorting to language generally reserved for imperialist opponents rather than communist friends.

Beijing’s response was unusually swift. “The Democratic People’s Republic of Korea has ignored the widespread opposition of the international community and brazenly carried out a nuclear test,” it said.

Long gone are the days when China and North Korea described their relationship as being “as close as lips and teeth”. Indeed, North Korea’s test has delivered China to a diplomatic crossroads: it can choose to act tough with a troublesome neighbour or to stick with the cajoling and persuasion that have now been seen to fail.

North Korea’s Government may not have changed, but China is eager to demonstrate that it is a mature player in world diplomacy. It is the only country that has a chance of exerting some influence on North Korea, yet Pyongyang has defied all its exhortations.

That China is furious at the test was more than reflected in the tone of its official response. Beijing had urged Pyongyang only a day earlier not to take such a provocative step.

Zhu Feng, an expert on North Korean ties, said that the statement showed China’s increasingly tough policy towards a country that was once its closest ally. “This is a very significant signal,” he said.

Now China may have to open a new chapter in its diplomatic coming-of-age. Beijing was exasperated, if not embarrassed, at Pyongyang’s decision nearly a year ago to drop out of the six-party talks that China had nurtured. They brought China, North and South Korea, the US, Japan and Russia to a table in Beijing to try to avert just such a crisis.

If the Chinese are to follow through on the rhetoric that such a test is unacceptable, they may have to contemplate backing UN Security Council sanctions rather than following the long-favoured policy of abstaining on sensitive votes.

China’s actions matter since it is the only friend to its communist cousin. It provides 33 per cent of all North Korea’s imports and is believed to account for 70 per cent of the country’s oil needs and much of its grain imports — all at knock-down prices.

However, assistance is no longer provided out of good-neighbourliness but because Beijing fears that North Korea’s collapse would trigger a flood of refugees across its border and create instability along its northeastern flank.

China can cut off the aid, and has done. It briefly closed the oil pipeline in 2003 for maintenance, and Pyongyang was quick to return to the six-party talks. That now may be less of a lever. Chinese cereal exports to the North slumped in the first seven months of this year to less than a third of their 2005 levels. Imports, too, have shrunk. If China failed to deter North Korea from testing, it is unclear how much leverage it has through traditional means.

If Beijing is not to find itself too far out of step with much of the rest of the world, it may even be forced to consider sanctions. It is a measure that Beijing abhors because of its foreign policy principle of non-interference. But North Korea’s latest show of brinkmanship may push China into uncharted diplomatic territory.

Zhang Liangui, an expert at the Central Party School, said: “China should adjust its policies, including reconsidering aid. At the Security Council, China will have to consider backing sanctions.”

China could choose to stick with words rather than action. But it knows it runs the risk that Japan, and possibly Taiwan, will move to defend themselves by activating their own nuclear programmes. The future stability of the region may force China out of its comfort zone of non-action. Only last week China’s UN Ambassador, Wang Guangya, said that no country could expect to be protected if it indulged in “bad behaviour”.

Yan Xuetong, Professor of International Relations at Tsinghua University, said: “If it just accepts North Korea as a nuclear power, Japan and South Korea might seize the opportunity to go nuclear. It would be a bigger problem that escalates the security flashpoint in Northeast Asia.”

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