Nakajima aims to be Japan's No. 1

Honda-backed Sato, Japan's most successful Grand Prix driver, helped struggling Super Aguri to ninth place overall this year.

However, 22-year-old Toyota protege Nakajima, son of former racer Satoru, will be competing for the team that finished fourth.

"It would be nice for me to be the top Japanese driver but to achieve that I have to push a lot, even if I am in a good team," he told Reuters in an interview.

"But that's the target and that's what I want to achieve for next year."

Nakajima will be partnering Germany's Nico Rosberg, also 22, and he recognised it will be quite some challenge to be up against a youngster rated as one of the sport's future front-runners.

"It's really great to work with Nico, he's going to be a really good benchmark for me," said Nakajima.

"Driving-wise there are many things to learn from him and it will be nice if I can push him and we can learn from each other."

The two have something in common already, forming the only line-up in the sport comprised of two sons of former Grand Prix racers.

Nakajima senior made his debut in 1987, the year after Finland's 1982 world champion Keke Rosberg retired.

Nakajima said his father, who runs a team in Japan's Formula Nippon and is unlikely to attend many Grands Prix other than on home soil at Fuji, was delighted to see another generation entering the sport.

"He is from a different era but from a driver's point of view there are some similar conditions," he said. "I think he is going to give me some advice but not too much."

The new Williams driver said doing better than his father, whose best race placing was fourth in five seasons in Formula One, was another of his ambitions.

"I really hope to achieve that and maybe it is going to be difficult in the first year but I want to achieve that in my career," he said.

Nakajima, who made his race debut at last month's season-ending Brazilian Grand Prix after Austrian Alexander Wurz announced his retirement, said he was ready to step up.

"I think I am ready for Formula One. I showed some good signs in Brazil," he said.

"It's going to be a really big challenge, because we do not have traction control and all the systems will be changed, but I think its a good chance for our team and for me.

"I was racing in GP2 this year and it's definitely not going to be a disadvantage for me not to have traction control. Hopefully it's going to be an advantage for me, so I'm really motivated for next season."

"It's difficult to set targets, results-wise," he added.

"It's going to be the first year and I just want to do my best job in the first season and to learn everything that I need. I want to show steady progress through the season and then I think the results will follow automatically."

Nakajima said his contract had been agreed between Williams and Toyota and he had no idea of the duration beyond next season.

"It's a bit complicated but for me personally it doesn't matter," he said.