Under Ermotti, who returned to UBS last year after it bought Credit Suisse in an emergency rescue, Switzerland's last remaining global bank faces a pivotal year in which it must combine IT systems and migrate clients from Credit Suisse - tasks that could make the next stage of integration trickier than the period until now.
"For us, the real risk is to have to delay the realizations of synergies," Ermotti told Reuters in an interview in Zurich.
"So in that sense, of course, we need to plan and to be credible in what we do. I'm confident that we are moving in the right direction, but we are not complacent," he said.
Migration of Credit Suisse clients to UBS platforms begins this year, and a target of decommissioning 30% of Credit Suisse apps would be the "maximum" achievable in 2024, he said.
UBS expects $13 billion in cost savings from the merger, which Ermotti said would mostly come from reducing staff numbers but also from merging IT systems.
UBS has seen its shares soar since the takeover, with investors upbeat about the prospects for the combined group given low acquisition costs, a huge increase in assets and an integration process that has so far gone relatively smoothly.
Ermotti refused to be drawn on how many people would lose jobs, saying only that it would be a "painful exercise". The bank, which employs more than 111,000 people, will try to reduce workforce through early retirements, attrition and outsourcing where possible but job cuts were "inevitable", he said.
NOT TO OVERSHOOT
Aside from the challenges of integration, UBS also faces regulatory and political headwinds, as Swiss authorities seek to safeguard the banking system and improve policing of lenders.
Ermotti said that while he agreed with most of the government's recent proposals to make Swiss banking safer, he did not agree with plans to make UBS hold more capital.
"When you talk about the only areas where we believe it's appropriate not to overshoot is the areas around capital," he told Reuters.
"Switzerland benefits from having a strong financial system, a strong competitive UBS is part of that equation and UBS stakeholders also benefit from being a Swiss-based company," he added.
He said that through its acquisition of Credit Suisse, UBS was already having to put aside $20 billion extra in capital.
($1 = 0.9268 euros)
