(Adds detail about investment bank)
ZURICH, Oct 25 (Reuters) - UBS AG Chief Executive Sergio Ermotti said on Thursday he cannot categorically exclude a large acquisition but such a deal is unlikely, given limited options for a potential tie-up.
"It is difficult to rule out M&A," Ermotti told investors after the company released third-quarter results, adding options for a transformational deal with a big partner are limited.
Ermotti addressed the prospect of a big deal after speculation in September in German media about a potential tie-up with Deutsche Bank, a suggestion that was dismissed as "fiction" by the loss-making German lender.
Speaking to potential speculation on his future at the Zurich-based bank, Ermotti said, "As long I have energy and passion for what I do and people believe it is OK, I will do it."
In September, UBS appointed Piero Novelli and Robert Karofsky as joint heads of its investment bank after veteran Andrea Orcel joined Spanish lender Santander as chief executive.
Novelli said on Thursday he is confident the pair will function well in the dual role, calling it the best solution for the transition following Orcel's exit.
"We complement each other and work well together," Novelli said. (Reporting by John Miller and Angelika Gruber Editing by Alexandra Hudson)