Euro zone finance ministers may achieve a "breakthrough" on Wednesday in their talks in Brussels on reforming supervision of Europe's banks, a German government official said.

Germany and France have been at loggerheads over how many banks the European Central Bank should directly supervise and some other details.

"We hope for major progress and perhaps a breakthrough (in the talks)," the German official said, speaking on condition of anonymity, adding that Finance Minister Wolfgang Schaeuble had told the German cabinet he was "optimistic" about a deal.

"We are ready to contribute to a solution on banking supervision. We have some questions but if they can be resolved by finance ministers today then Germany will not stand in the way of an agreement," the source said.

(Reporting by Stephen Brown, writing by Gareth Jones)