He reiterated that he saw 20,000-30,000 job cuts in the event of a merger and said a possible conflict with unions over any merger could present significant costs to the banks.

"We will watch this very critically, and also with an eye to our possibilities in the supervisory boards of Deutsche Bank and Commerzbank," Bsirske told reporters. "No one can reasonably expect that this will just be watched from the sidelines if 20,000 to 30,000 jobs are at risk."

(Reporting by Andrea Shalal; Writing by Madeline Chambers)

Stocks treated in this article : Deutsche Bank, Commerzbank