Since China joined the World Trade Organisation in 2001, its bilateral trade surplus with the US has doubled from $83bn to more than $160bn last year. In the face of growing protectionist pressures in Washington generated by that imbalance, the new US trade representative, Rob Portman, took the job last April promising a ?more aggressive approach? on China.

Yet, so far, Washington and Beijing have been able to manage those pressures, doing just enough on a series of nagging trade issues to keep the lid on congressional demands for much tougher actions.