"I am 100 percent sure of Toyota's potential and of its chances of challenging for the Formula One World Championship," the 32-year-old said in a team statement at the German Grand Prix on Friday.
"I am therefore more than happy to continue my excellent relationship with the team into the longer term and to try to achieve our common goals."
Toyota already have Germany's Ralf Schumacher under contract, leaving them with an unchanged line-up for next season.
