Rossi is well on course for his fifth straight world title

The Italian, 26, won the title in his first season with Yamaha last year and is now on course for a fifth in a row.

"I am so happy to be able to announce the continuation of my relationship with Yamaha," said Rossi.

"Last year was magic, to win my first race with Yamaha and then to win the championship. It just made sense to stay with Yamaha for another year."

Yamaha managing director Lin Jarvis said: "This year is the 50th anniversary for Yamaha and is therefore a very special year us.

"We hope our MotoGP efforts will culminate in a second world title for Valentino.

"The partnership with Valentino is the key point that will now allow us to proceed with our total MotoGP strategy for 2006."

The London-based rider was rumoured to be contemplating a move to Formula One but has ruled it out for now.

"I'm quite sure I will still be racing MotoGP motorcycles when the new rule changes come in for 2007," he said last month.