FRANKFURT - Daimler AG's supervisory board is set to approve a three-year extension to CEO Dieter Zetsche's contract on Wednesday, a source familiar with the matter told Reuters.

Though some German media had speculated about Zetsche's future, his internal standing was never in doubt and some company insiders believe his contract could be extended beyond 2013.

"It's not as if when the three years are up it's over for him. He's not that old," the person said on Tuesday.

A spokesman for Daimler declined to provide a statement. The company traditionally has a policy of not commenting either on boardroom matters or personnel issues.

Zetsche turns 60 in May 2013, an age at which rival BMW AG permits board members to extend their contract only by one-year intervals, if at all.

Zetsche's success in steering the company through the crisis in the global premium car and commercial vehicle market will largely determine whether he stays on or hands over the reins, most likely to Wolfgang Bernhard.

Bernhard replaced Rainer Schmueckle earlier this month as head of production at premium division Mercedes-Benz Cars. That was the second key management change following the resignation of sales chief Klaus Meier last September. He was replaced by Joachim Schmidt.

Zetsche, who also serves as CEO of Mercedes, has been a supporter of Bernhard ever since they first formed a duo at Chrysler in 2000. He prominently criticized a decision by predecessor Juergen Schrempp to force Bernhard's departure four years later. Bernhard was in line to be Mercedes CEO.