Chinese anger at Rio Tinto for reneging on a deal with aluminium group Chinalco and opting instead for an iron ore joint venture with BHP Billiton last month was understandable. Indeed, China has good reason to question the Rio-BHP JV on competition grounds.

But the detention of four Rio Tinto employees – on suspicion of espionage according to Australia’s foreign minister — bang in the middle of sensitive negotiations on iron ore exports to China is a
dangerous step in the wrong direction. Beijing must either justify the arrests publicly or release the Rio staff immediately.