Brief and to the point: the letter Timothy Geithner wrote last week to Michel Barnier, a copy of which can be viewed through a link to this article, was diplomatic but left not doubt about America's anger over with the way the European Union is attempting to regulate private equity and hedge funds.

The one-page letter is framed with diplomatic niceties: "Please allow me to extend my congratulations on your new position", it starts, and it ends with "I look forward to working with you".