Button reckons Force India will pose a good challenge this season

Formula One world champion Jenson Button thinks as many as seven teams could be battling it out throughout 2010 for the end-of-season honours.

"I think there are more than four teams at the front," he told Reuters Television at his team McLaren's base in Woking outside London on Monday.

"You've got us, Ferrari, Mercedes and Red Bull, but you've also got Sauber, Force India are not far behind, and the Williams. So it's very, very competitive, which is good to see."

Compatriot and team-mate Lewis Hamilton, the 2008 world champion, finished fastest in the final pre-season testing session in Barcelona on Sunday just ahead of Red Bull's Mark Webber and Ferrari's Felipe Massa.

Seven-times world champion Michael Schumacher of Mercedes came in sixth despite being out of the sport since 2006, and Hamilton cannot wait to pit his skills against the 41-year-old German.

"To be on the same track as him will be a really cool feeling," he said, a broad grin breaking out on his face.

"He's a legend in the sport."

Button, like Hamilton, was eager to get the season underway at the Bahrain Grand Prix on March 14.

"I'm going to be a part of it all, which is great. Going into the race with the number one on the car, what a challenge," he said.