David Usborne: Onus on China to put pressure on its barmy neighbour

The conclusion of the international panel of investigators that the sinking of the South Korean corvette was thanks to a torpedo from a North Korean submarine comes as a surprise to no one. But almost everyone – Seoul, Beijing and Washington especially – will be wishing something else had been responsible.

But there are no icebergs in those waters and here we are again confronting an almost inexplicable act of aggression by Pyongyang. The best you could say is that the sub crew bungled and never meant actually to hit the ship, which sank with serious loss of life. Western capitals will be less charitable. Pyongyang seems again to be calculating that the best way to distract its people from their misery is to show off its ability to bring the entire peninsula to the brink.

The renewed flaring of tensions is ill-timed for the US Secretary of State, Hillary Clinton, who yesterday embarked on a long-planned visit to Japan, South Korea and, most importantly, China. She will head a delegation in Beijing of some 200 US officials, including cabinet members, with issues to address ranging from trading issues, Iran sanctions, currency tensions, climate change and military ties.

Now she is in a predicament. The US was swift to call the sinking an unacceptable "act of aggression" and will support South Korea in condemning Pyongyang and bringing the issue to the UN Security Council, probably on Monday. But China has so far shown its usual reluctance when it comes to calling the regime in Pyongyang what it really is: a cruel and self-isolating socialist dictatorship.

Mrs Clinton, who was criticised after her first visit to China last year for playing down human rights issues in favour of a stronger Sino-American partnership, will doubtless express her disappointment. China is the only country in the world with some window into the mysteries of Pyongyang and some leverage over it. Only recently, North Korea's Kim Jong-il had talks in Beijing.

Privately, Mrs Clinton will urge China to get tough, particularly given the seemingly solid proof of North Korea's latest misdeed. Pushing Beijing carries risks. It has only been in the past few days that it swallowed its reservations and endorsed the US push for Iran sanctions. It may not be ready for any more American bullying.

China has long been cultivating a new image as a responsible world power. Abandoning its traditional coyness when it comes to Pyongyang would help convince many people, including Mrs Clinton, that it is ready to play that role with a degree of seriousness and consistency. But there is little evidence that the Chinese will do any such thing but will instead be guided by narrower concerns. Its priority for a long time has been maintaining the status quo on the Korean Peninsula, regardless of how barmy Pyongyang becomes.

Watch for this to be pushed into the netherworld of the Security Council in New York. Action will not come quickly, because as alarmed as Western nations may be about North Korea, passing sanctions on Iran must happen first. And unless it has completely lost the plot, Pyongyang will stay quiet for a while.