The US Treasury has told the Chinese authorities that they must revalue their currency by at least 10 per cent against the dollar to prevent protectionist legislation in the US congress.

Henry Kissinger, former US secretary of state, is one of a number of unofficial envoys who have impressed upon China the urgent need for action on the 10 per cent target, and on the seriousness of the threat from Congress, people with familiar with the administration's efforts said.