US Treasury Secretary Timothy Geithner has warned the European Commission that its proposals for more restrictive regulation of alternative fund managers could affect cross-border investment, demonstrating how the controversial European Union directive could have transatlantic ramifications.

According to Paul Myners, the UK financial services minister, Geithner had raised the issue of the Alternative Investment Fund Managers directive in a letter to Michel Barnier, who was confirmed as European commissioner for the internal market last month. Myners mentioned the letter at a breakfast briefing, which was organised by the British Private Equity and Venture Capital Association.