UBS AG (UBS) Chief Executive Oswald Gruebel addresses clients, employees and the public in an unusually personal message as part of "we will not rest," which is the Swiss bank's most extensive advertising campaign in two years.

"I have often asked myself why; why me; and why return from retirement, until it became clear to me that I had to do it for the employees, for the bank who was once our toughest competitor, and for myself," UBS CEO Gruebel says in the taped message which went live on UBS's website Sunday.

In an unconventional move, Gruebel, who ran UBS's biggest domestic rival Credit Suisse Group (CS) until 2007, was enticed out of retirement in February of last year to run UBS, shortly after the bank was propped up by a government-led financial aid package.

Gruebel, who has ushered in UBS's return to profitability, overseen a dramatic slowing of wealthy client outflows, and outlined mid-term targets including roughly CHF15 billion in annual pretax profit, is shown in a variety of settings in the spot, including walking along Zurich's lake, speaking to an audience together with Asia head Chi-Won Yoon, and in meetings with close deputies such as COO Ulrich Koerner and risk head Philip Lofts.

"This is much more than an ad campaign--it is an expression of our ambition, our stance, and our responsibility, beginning with me," Gruebel says in the spot.

UBS wasn't immediately available to comment on how much the ad campaign cost.

-By Katharina Bart, Dow Jones Newswires; +41 43 443 8043; katharina.bart@dowjones.com