UBS Chief Executive Sergio Ermotti on Friday warned of painful decisions about job cuts following the takeover of Credit Suisse.

"We won't be able to create, short term, job opportunities for everybody. Synergies is part of the story," Ermotti told a financial conference in Bern.

"We need to take a serious look at the cost base of the standalone and combined organisations and create a sustainable outcome," he added. "It will be painful."

Switzerland's no. 1 bank, which agreed in March to take over its smaller Swiss rival as part of a rescue orchestrated by Swiss authorities, has said it aimed to close the deal quickly with Ermotti saying on Friday he hoped it could be done in the next few days.