BMW chief Gerhard Berger believes engines will be the key to this season's title battle - and boasted that the Grove-based Williams team have the best on the grid.

The former McLaren and Ferrari driver retires this week as head of BMW's motorsport operations, which is providing Williams with engines which he claims are without equal in Formula 1.

Berger is confident the BMW engine's power will enable title challenger Juan Pablo Montoya to race without fear of breaking down.

He said: "Our engine is the measure of all things in Formula 1. Thanks to our development programme, we have been able to introduce new components in each of the races and therefore don't have to concentrate on considerably increasing the engine's horsepower.

"Our advantage is that we can mainly concentrate on the reliability of the engine."

Montoya is a point adrift of championship leader Michael Schumacher with just three races left, with Kimi Raikkonen a point further behind in third.

Berger believes Montoya needs to become less emotional in the cockpit - although the Austrian admits even he is in awe of the former CART champion's abilities.

He said: "He draws so much energy from his emotions, which also sometimes represent an obstacle to him. He is terribly fast. His special talent is overtaking."