Plans are being drawn up in Brussels that are set to see tougher restrictions placed on the activities of hedge funds, with suggested rules including only allowing these investment vehicles to use locally-based banks.
The proposals, drawn up chiefly by France and Germany, have already caused ruptures within Europe, with the UK believing it is an attempt to curb the country's dominance of the financial services industry, reports the Financial Times.
Lord Myners, the UK's financial services minister, has already pledged to fight the plans "line by line and minute by minute".
Mr Geithner has now weighed into the debate - sending a letter to Michel Barnier, Europe's internal market commissioner, stating that international cooperation on regulation is needed.
He also warned that the EU proposals could be seen as discriminatory if hedge funds inside the EU are not allowed to access funds from outside the bloc.
The European Parliament is also currently considering plans to defer up to 60 per cent of banking bonuses for a three-year period.
By Claire Archer