Itau's remarks came after newspaper Valor Economico reported earlier in the day that Schwab was considering such a deal following the Brazilian bank's purchase of an 11.36% stake in XP two weeks ago.
The report, citing sources, said the U.S.-based company would be one of those interested in the transaction. Nasdaq-traded shares of XP soared after the report.
"Itau Unibanco denies it is in contact with Charles Schwab," the lender said in a statement through its press office.
Schwab said it would not comment "on rumors or speculation."
XP did not immediately respond to a Reuters request for comment.
(Reporting by Carolina Pulice in Mexico City and Gabriel Araujo in Sao Paulo; Additional reporting by Mehnaz Yasmin in Bangalore; Editing by Chris Reese, Leslie Adler and Bernard Orr)