The war of words between Beijing and Washington over cyberespionage has escalated, with the US accusing China of trying to break into government computer networks to obtain information that would help its defence industry and military planning. It is the first time the Pentagon's annual report on China has explicitly claimed that it is targeting government networks. Until now US officials have tended to focus their public comments on the hacking of private business networks, though these include defence contractors. The Foreign Ministry dismissed the claim as groundless and unhelpful to mutual trust and co-operation.

The finger was pointed at the PLA, which responded in its official newspaper by branding Washington the "real hacking empire". Given that the US, as the inventor of the internet, could be expected to be at the forefront of cyberespionage technology, there may be more than a grain of truth in that.

The tit-for-tat claims sound like Sino-US rhetoric on trade and human rights issues, with key words changed. But the escalation is real enough. The Pentagon said the information targeted could benefit China's arms and technology sectors, help military planners build a picture of US defence networks and reveal US leaders' thinking on China-related issues.