Nico Rosberg feels it is 'too early' to call Mercedes 2014 World Champions

Mercedes' Formula one driver Nico Rosberg has said it was 'too early' to call Mercedes team favourite for the 2014 World Championship, despite setting two fastest times of the pre-season test in Bahrain with teammate Lewis Hamilton.

The German racer was reportedly 1.627 seconds quicker than the first non-Mercedes driver but added that it was impossible to compare lap times during testing because every team run different programmes at different times.

According to the BBC, Rosberg said that they did qualifying-style practise and the other teams had not burnt as much fuel as they did but it was still early to tell who had the fastest car.

Rosberg also admitted being ahead of the world champions Red Bull because they were struggling whereas Mercedes had done many more laps and uncovered many more problems, which would all be sorted by the team they arrived at Melbourne.

Formula one has introduced new 1.6-litre hybrid turbo engines and told the teams not to use more than 100 kilograms (160 litres) of fuel, which Rosberg said were difficult to adopt, the report added.

Rosberg also said that the biggest challenge was all the new systems with hybrid power while pointing out that Bahrain's Shakir track was one of the most demanding in terms of fuel consumption, which proved it to be an effective circuit for testing.

Rosberg said that it had been difficult completing the race within those100 litres of fuel and felt sure that everybody else was also struggling with the same problem.