Jenson Button has claimed that Williams and Mercedes are the teams to beat ahead of the opening race in the Formula 1 season.

The McLaren driver believes that the two teams have managed to avoid suffering major problems during the winter preparations and insists they are ahead of their rivals heading into next week's race in Melbourne.

"It has been a messy winter for a lot of people in terms of mileage on circuit," Button told Sky Sports News. "The two that you would pick out that look strong and consistent are Mercedes and Williams.

"In a way it is not good when you are behind certain teams, but I am happy for Frank Williams that they have a competitive car so far this year. I think those are the two teams to beat right now."

Defending champions Red Bull have been hit by a number of problems in pre-season testing.