ZURICH (Reuters) - Swiss banking giant UBS will look for merger and acquisitions opportunities in the United States in the years to come, its chairman told the NZZ newspaper on Sunday.

UBS, which took over former rival Credit Suisse last June, wants to expand its U.S. wealth-management business through potential M&A in three or four years, Colm Kelleher said.

"Only in wealth management and not yet," he added.

Since rescuing Credit Suisse, UBS has faced criticism over a $1.6 trillion-plus balance sheet that is nearly twice the size of the Swiss economy and has prompted the country to review its regulation of systemically important banks.

Kelleher, however, pushed back against calls for UBS to be subject to higher capital requirements.

"If you have too much capital, you penalise the shareholders, but also the customers because banking services become more expensive," he told NZZ.

The first merger of two systemically important global banking groups also resulted in the return of former boss Sergio Ermotti for a second stint at the helm.

Kelleher said Ermotti is the right person for the "Herculean task" of integrating Credit Suisse, adding that he would like Ermotti's successor to be someone from within UBS.

(This story has been corrected to show M&A is envisaged in three or four years' time, not over the next three or four years, in paragraphs 1 and 2)