FRANKFURT, Germany (AP) — A top European Central Bank officials says the ECB should be responsible for supervising the biggest financial institutions under plans to make it Europe's central banking supervisor.

Joerg Asmussen said in a speech text it was "reasonable at least at first to limit European oversight to institutions that are systemically relevant nationally and Europe-wide."

That means banks that are so big that their failure could threaten the entire financial system of a country or of Europe.

EU internal markets commissioner Michel Barnier advocates making the ECB supervise all banks eventually; Germany's Finance Minister Wolfgang Schaeuble says it should focus only on the biggest.

The EU's executive commission is to unveil proposals for an ECB supervisory role on Sept. 12 as a measure against the eurozone debt crisis.