UBS has brought Sergio Ermotti back as chief executive to steer its takeover of Credit Suisse.

Ermotti, who was chief executive for nine years before stepping down in 2020, will replace Ralph Hamers, UBS said on Wednesday. Hamers will remain as an adviser during a transition period, the Swiss bank said.

UBS said it acted “in light of the new challenges and priorities facing UBS after the announcement of the acquisition” and cited Ermotti’s previous experience including a restructuring of its investment bank.

“This unique experience, together with his deep understanding of the financial services industry in Switzerland and globally, make Sergio Ermotti ideally placed to pursue the integration of Credit Suisse,” UBS said.

The announcement comes less than two weeks since UBS agreed to take over Credit Suisse in a $3.25bn weekend rescue deal supported by Swiss authorities.

In a statement, Hamers said he was “stepping aside in the interests of the new combined entity and its stakeholders, including Switzerland and its financial sector”.

“Integrating Credit Suisse is UBS’s single most important task and I am confident that Sergio will successfully guide the bank through this next phase. I am of course sorry to leave UBS, but circumstances have changed in ways that none of us expected,” Hamers said.

Hamers had been chief executive since November 2020.

UBS chair Colm Kelleher said Hamers had put the bank “in a position to stabilise Credit Suisse and ensure a successful integration”.

“While the acquisition will support UBS’s existing strategy, it imposes new priorities on us,” he said. “With his unique experience, I am very confident that Sergio will deliver the successful integration that is so essential for both banks’ clients, employees and investors, and for Switzerland. I know Sergio will hit the ground running.”

Ermotti will leave Swiss Re, the reinsurer where he is chair.