Button: It's a seven-way fight in 2010

Defending champion Jenson Button has backed the 'big four' to fight for honours during the 2010 F1 season - but has suggested that three other teams could join the party during the season ahead.

Speaking to Reuters following the final pre-season test in Barcelona, Button said he felt that his own McLaren team - as well as Ferrari, Mercedes and Red Bull Racing - would be a contender during the year ahead as the four top teams from 2009 look to fight for the crown.

However, with a number of other teams having impressed during pre-season testing, Button suggested that another three teams could realistically be regarded as potential winners for the year ahead.

"I think there are more than four teams at the front," he said. "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."

Team-mate Lewis Hamilton set the pace during the final pre-season test in Barcelona, but Red Bull, Ferrari, Force India, Williams and Mercedes all had cars inside the top ten on the overall times.