UBS AG's organizational and operational restructuring is on track, but the Swiss bank's efforts to renew client trust will require long and hard work, Chief Executive Oswald Grübel warned.

In a memo sent Tuesday to the bank's more than 70,000 staff, Mr. Grübel said that "returning the group to profitability will only be the beginning." He warned that "the recovery of our reputation will require hard work and relentless effort."