Ms Brainard's comments follow remarks earlier in the day from the head of Germany's influential Bundesbank, who warned eurozone politicians to stay away from talking down the euro, arguing that any policy to weaken the currency would lead to higher inflation.
Some insiders have suggested to me that Mr Obama might plug this gap by promoting Lael Brainard, the Treasury's senior international official, to be Mr Lew's deputy, with an understanding that she would now take the lead in the administration on most international economic issues.
The Mayor of Carmel, Jim Brainard, has become America's evangelist-in-chief on the matter, demolishing 78 sets of traffic lights and replacing them with those round islands so familiar to drivers in the UK. Four more will be finished in the coming months.