At last, the mountain moved. After months of subtle diplomacy from the US Treasury and not so subtle threats from Congress, China two weeks ago grudgingly gave its currency, the renminbi, a little more freedom to rise.

The exchange rate issue dominates a relationship that will shape the future of the world economy – the confrontation between the US, the economic superpower of the 20th century, and China, the rising industrial hegemony of the 21st. Washington, with occasional support from Europe and selected emerging markets, says Chinese currency policy unbalances the world economy and disadvantages foreign companies.

But even if the currency rises significantly, as the White House demands, the US still faces myriad challenges managing its trade and investment relationship with Beijing.