Seven-time world champion Michael Schumacher says he is "totally fired up" for a return to Formula One racing next year with Mercedes GP, DPA reported.
Schumacher said he had agreed to a three-year deal with the Silver Arrows team alongside Nico Rosberg in an all-German driver line-up.
Explaining on his website why he had decided to return to racing after a three-year absence, Schumacher said the idea of a German F1 team "extremely tempts me", while working together with team principal Ross Brawn again also played a major role.
"Above all, however, my old hunger for racing is back," Schumacher said.
"In Abu Dhabi (at the last Grand Prix of 2009), when Ross asked me if I could imagine returning to F1, I felt that I wasn't ready for it. But only two weeks later, when he called me once again, I realized that my old passion was returning.
"Suddenly I was on fire again. For me, the imagination to be back in a F1 car and to compete for the world championships is exciting and extremely inspiring."
Schumacher said until recently he was absolutely sure he had ended his racing career.
"But sometimes things change suddenly and unexpectedly. All of a sudden, the framework conditions aren't the same anymore," he said.
"At that point, you have to reconsider the decisions you've made. And, to tell the truth, the failed comeback attempt (as stand in for Felipe Massa) last summer gave me reason to reconsider my situation.
"I was surprised myself how fast and how strong I committed myself to this topic again. Apparently, my batteries recharged completely during the last three years. And when - thanks to Ross - the opportunity arose to drive for Mercedes GP, I realized that my old motivation was back, full of fresh energy and great force."
Schumacher thanked his old team Ferrari, where he was working as an adviser, for not standing in his way, and said he was physically fit.
After specific exercises he had no more concerns about the neck injury suffered early in the year in a motorcycle accident which had put a stop to the return as replacement for Massa in a Ferrari.
He also had no doubts the new Mercedes GP team, which takes over from the championship-winning Brawn team, would be strong.
"The relation between the competence of Mercedes and the current world champion team is extremely attractive and promises a good performance. I think the duels on the race track will be electrifying," he said.
Schumacher said his decision was also supported by his wife, Corinna, who "appreciates my passion".
"When I told her about my plans, she immediately felt that I am serious about it and she instantly gave her approval," he said.
"To put it simply: I'm totally fired up for next year!"