F1: Lewis Hamilton and Nico Rosberg admits battle for F1 title will get in the way of friendship at Mercedes

Mercedes team-mates Lewis Hamilton and Nico Rosberg have made clear that friendship has its limits and theirs is likely to be tested to the full this year as they fight for the Formula One title.

The two have been friends and rivals since their early teens, racing go-karts together and following each other through the junior series with both winning the GP2 titles in successive years for the same ART team.

Germany's Rosberg made his F1 debut in 2006, Hamilton followed in 2007 and last year they again became team mates when the Briton moved from McLaren, the team with which he won the 2008 championship.

Rosberg won this year's season-opener in Australia and leads the championship after two races, 18 points clear of second-placed Hamilton who triumphed last weekend in Malaysia.

"At the moment it hasn't changed at all," the son of 1982 world champion Keke Rosberg said at the Bahrain Grand Prix when asked about the dynamics of their relationship at Mercedes.

"Maybe because we are not thinking about the championship yet, just race by race really just making the most of what we have, winning races. So early days, maybe," he told reporters.

Rosberg recognised that could change as the season progresses, but was not concerned.

"We've been in this situation before. In go-karts we were fighting for the championship there, it's exactly the same," he said. "A little bit more people around, more media and spectators but exactly the same in the end.

"We managed to get through there with respect and I'm confident we are going to manage again in any circumstance. There will be tough times, inevitably, but I'm confident we can work through it and we will."

Very few drivers have real friends on the starting grid, with team mates the ones they want to beat more than anyone since they have the same equipment and provide the clearest yardstick to performance.

Some teams have clear hierarchies, such as Ferrari in the Michael Schumacher era or Red Bull where Sebastian Vettel has been champion for the past four years, and any 'team orders' in favour of one driver can trigger resentment and controversy.

Mercedes, whose car is clearly a step ahead of the rest at present, are being closely watched for signs of fallout between drivers whose relationship has been hitherto harmonious.

Hamilton indicated nobody should be under any illusions about the reality.

"It's very simple," he told reporters. "People are constantly talking about us being friends and all that stuff.

"Nico and I, as with anyone, can count our friends on one hand. Nico does not come into those five friends I have, and I don't come in the five friends he has.

"We're colleagues who have known each other for a long time, longer than any of the other drivers, and we have a great amount of respect for one another. We work in the same team and we have a great working relationship.

"We've raced since we were kids, we've been team-mates, been at the front of the championship in the past several times in karting and different championships, and it is no different then as it is now."

While both might be steeling themselves for the future, they were also revelling in the transformation of their team from runners-up to front-runners and being a part of that success.

"It's great. I've never had that before in F1 and to come to the track where I know I've got the best car and can win the race is a great feeling," said Rosberg.

"To be a part of the whole momentum that we have as a team. It's a special moment."

Reuters