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Lewis Hamilton says he is excited by the challenge ahead with Mercedes.

The 2008 world champion leaves McLaren at the end of the season having signed a three-year deal to drive for Mercedes from 2013, rather than stay with the team he joined at 13.

The 27-year-old Briton told 91�ȱ� Radio 5 live: "The deals were very similar, it is more about the challenge for the future.

"I have a much steeper hill to climb, with new people and it is exciting."

Hamilton denies he has taken a risk by deciding to leave an established McLaren team for one with just a single win in the past three seasons.

"Lots of people have opinions about whether it is good or bad, at the end of the day I had to do what I felt was right for me," he added.

"Through my whole life I have always been a risk taker, someone who did not take the easy route, I have always made it harder for myself.

"I am going from a top team, I could have stayed, it would have been very, very easy to stay. They asked me several times over the course of the year to stay."

However, he accepted he is unlikely to be challenging for the title next season.

"I definitely go there with a very open mind and very much aware that the car I am leaving could be the best, probably will be the best," said Hamilton.

"I wish the team all the success for next year. I am still part of the team now so I want to focus on the good times now and the good times we will hopefully have in the next six races.

"I am very much aware next year could be very tough, where we are not winning at all but hopefully I can change that."

Speaking ahead of this weekend's Japanese Grand Prix at Suzuka, he likened leaving McLaren to leaving home.

"I have nothing but love for this team," he said. "I grew up here and had a wonderful experience here and now it is just about having that next step, which I guess is the last step of my independence.

"I have moved out of home and I am now moving out of my home team and experiencing something new."

Hamilton also would not rule out a possible return to McLaren in the future.

He said: "This is me walking over the bridge that was built over the years, rather than burning that bridge down.

"If my road brings me back one day across that bridge I will know I have had the most incredible times already to have many memories of."