BERLIN: Seven-times world champion Michael Schumacher said Thursday he does not expect to win the world drivers championships in his first season back, but wants to win an eighth title within three years.

The 41-year-old has signed a three-year deal to come out of retirement to race for German stable Mercedes GP having last contested a Formula One race in 2006 for Ferrari.

"In our long-term targets with Mercedes, we have a clear objective: I want to become world champion again," Schumacher told Bild.

"Perhaps that will not happen in my first season back, but it is realistic over the three seasons (his contract runs until 2013).

Before his retirement in October 2006, Schumacher won 91 Grand Prix races and he admits he has missed the buzz of Formula One driving, although he only considered a return to the track last year.

"When I went to Formula One races (after retiring), I was more annoyed than frustrated not to race," said the German.

And despite his advancing years, 'Schumi' says age will not be a factor when he returns to racing on March 14 in Bahrain.

"Apparently, I have succeeded in pushing back the effects of aging, I must have good genes," said Schumacher.