"I will rule out absolutely nothing," Deutsche Bank chief executive Josef Ackermann told reporters in Berlin, when questioned over its reputed interest in the postal bank.
Deutsche Post, the mail group which controls Postbank, has insisted it is currently not up for sale, but it may come on the market after the deregulation of Germany's postal system next year.
Postbank has almost 15 million customers and finance experts believe it is an attractive prospect among buyers.
Indeed Klaus Zumwinkel, CEO of Deutsche Post World AG, which owns a majority stake in Postbank, said that several banks had expressed an interest in the acquisition.
Earlier this year Commerzbank said it would be interested in making an offer for Postbank should it go up for sale.