One of the under-reported changes in the global geopolitical balance last year was America’s return to Asia. One of the worrying was the notable deterioration in the Sino-American relationship. On this much Barack Obama and Hu Jintao should be able to agree during the Chinese president’s upcoming visit to the White House.

It is when they turn to the “why” that things are likely to get tricky. “You started it”, has thus far been the shared refrain. So Mr Hu will be tempted to protest that the second of the two developments flowed from the first: the chill was a consequence of a US strategy to contain China. Mr Obama’s riposte will be that America’s diplomatic and military re-engagement in the region was an inevitable response to China’s decision to throw its weight around.

This, of course, is before the two leaders get to the economics. Most of the headlines from Mr Hu’s state visit next week will probably be generated by differences over trade and exchange rate policy. China’s huge trade surplus generates strong protectionist pressure in the US. Washington’s oft-repeated demand for revaluation of the Renminbi is seen in Beijing as unwarranted intrusion in China’s economic affairs.