Lewis Hamilton insists his move to Mercedes is not a gamble, despite admitting he will not be fighting for the Formula One title in 2013.

Hamilton, 27, will leave McLaren after a 14-year partnership when he makes the move to join the German marque on a three-year contract at the end of 2012.

While McLaren have won 16 races over the last three campaigns, including three of the last four, Mercedes have only Nico Rosberg's victory in China earlier this year to show for their efforts during the same period.

The reshuffle in driver line-ups, with Sauber's rising star Sergio Perez taking Hamilton's seat at McLaren and Michael Schumacher being forced out of Mercedes, is the talk of the paddock ahead of this weekend's Japanese Grand Prix at Suzuka.

There are plenty questioning 2008 world champion Hamilton's decision to switch from a team with a proven winning pedigree to one well off the pace of the top four in this season's constructors' championship.

But, when asked if he felt he had taken a risk in joining Mercedes from 2013, Hamilton said: "I don't. Not really.

"I've had such a great career with McLaren. I signed for McLaren when I was 13 and have had such an incredible journey with them.

"But in the end I had two offers on the table which were very similar but one was a lot more exciting. It's just a challenge.

"I could stay in the great car that I have, which I've worked really hard to help develop with the team, or go to a car that's not so well developed and help it."

He added: "No doubt it was one of the most difficult decisions I've faced in my life up to now.

"But a lot of other racing drivers, a lot of greats - (Alain) Prost and (Ayrton) Senna, they've all been with several teams.

"I don't think there is one who's been with one team for his whole career (1963 and 1965 world champion Jim Clark spent his entire career with Team Lotus).

"I'd been thinking for quite some time about what I wanted to do with my future, where I want to go, It's easy staying in the same place, but going somewhere else and taking on a new challenge is sometimes maybe even more exciting."

Asked if he felt he could battle for the title in 2013, Hamilton said: "No, I'm fully aware the car at the moment is not a world championship-winning car.

"The car that I'm in right now is a car that I've developed. Next year will be an evolution of the car that I've helped develop (at McLaren) and that will be a championship contender.

"But we (Mercedes) will work very, very hard to have a better year next year, but it takes time. You don't just arrive and things change. I think the focus is more long-term.

"If I can go there, help them progress, if we get some wins, if we eventually win the world championship - that's going to be an incredible feeling for all of us."