Maria Fekter said the figure was not as high as some had expected.
"It's about 100 billion euros that is needed for recapitalization," she said at an investor conference in Vienna.
EU and banking sources told Reuters earlier on Thursday that this was roughly the figure European Union member countries had agreed was needed. Europe's banks are on the verge of being recapitalized in an attempt to halt the euro zone debt crisis and restore confidence in the sector.
($1 = 0.725 Euros)
(Reporting by Michale Shields and Sylvia Westall)