Tokyo:Yamaha Motor Co. has extended its contract with seven-time motorcycling world champion Valentino Rossi through 2008, the company announced Thursday. Rossi, who turns 28 this month, will ride as part of Yamaha's Official Factory Team for another two seasons, Yamaha said in a statement. Rossi has won two MotoGP World Championship titles and 25 Grand Prix since joining the team in 2004, it said. "I'm very happy I renewed the contract with Yamaha until the end of 2008 so now I can just concentrate on racing this season," the statement quoted Rossi as saying. Rossi has won world titles in the 500cc, 250cc and 125cc categories, but was denied his fifth successive MotoGP title last year.