With policymakers failing to make progress on the critical issue of global imbalances, America has no alternative but to put China on notice. Privately but promptly, Washington has to inform Beijing it will label it as a currency manipulator, back legislation treating the manipulation as an export subsidy, and take it to the World Trade Organisation if it does not let the renminbi rise significantly.

The renewed increases in the external imbalances of the two main economies pose major risks. China’s surplus is again climbing while it tightens monetary policy because of concerns over overheating. It thus maintains its rapid expansion partly at the expense of other countries, and dampens global growth. It should instead let its currency rise and limit the cutback in domestic demand. That would help contain inflation, and offset the resulting decline in its trade surplus.

US output growth has been cut in half in the past six months by the renewed sharp expansion of its current account deficit. The Federal Reserve’s second round of quantitative easing and the likely extension of some form of the Bush tax cuts are efforts to provide offsetting boosts to domestic demand – but they may not succeed.