Mercedes is hoping to rekindle the fiercely competitive spirit that Lewis Hamilton and Nico Rosberg shared as go-kart rivals when they come together as Formula One teammates this season.

Speaking as a gleaming new W04 race car was unveiled under the sunshine of Andalucia, team principal Ross Brawn said "the dynamic" between the two Mercedes drivers will be very important.

"They*re good friends," he said, adding that the team now had a very competitive pairing.

First around the circuit in the new car was Rosberg, who said it felt very good and he could "straight away push hard."

The 27-year-old also said Monday that the change of partner, with Hamilton replacing seven-time world champion Michael Schumacher, was good.

Rosberg said "it*s a fresh start, we*re going to push each other."