Tidjane Thiam, 52, started work as CEO of Credit Suisse on Wednesday and investors are optimistic he can bring about a major change of strategy at the bank, though many also expect him to tap the market for cash.

"We will need a strong balance sheet that allows us to withstand adversity, while continuing to invest in the future," Thiam says in the memo, a copy of which was obtained by Reuters.

Choosing what the bank will do and where it invests its capital would be a clear focus in the weeks and months ahead, Thiam said, adding he would determine the strategy later this year. A spokesman confirmed the contents of the memo.

(Reporting by Robert-Jan Bartunek in Brussels and by Katharina Bart ande Joshua Franklin in Zurich; Editing by Michael Shields)