State Street did not immediately respond to a Reuters request for comment.
Credit Suisse Chief Executive Thomas Gottstein earlier in the day called queries over a potential takeover offer "really stupid", shutting down questions after a report by Inside Paradeplatz on the matter sent shares briefly higher on Wednesday.
Financial news blog Inside Paradeplatz had reported State Street would bid 9 Swiss francs a share for Credit Suisse, citing an unidentified source.
(Reporting by Niket Nishant in Bengaluru; Editing by Aditya Soni)