BARCELONA • A refreshed Lewis Hamilton insists he is prepared for the most gruelling Formula One season of his life as he attempts to deliver a third consecutive world championship for Mercedes.

The Englishman romped to the third world title of his career last season with three races to spare to see off team-mate Nico Rosberg.

However, having enjoyed his time off during the winter, the 2008, 2014 and 2015 champion is eager for more in F1's longest-ever, 21-race schedule this year.

"The highlight of the winter break has been the break! No racing - just family, friends and snowboarding," he said as Mercedes launched the W07 Hybrid on the first morning of pre-season testing in Barcelona yesterday.

"I love racing, so I welcome more races, but it's going to be a gruelling season with 21 rounds."

If Hamilton, who was outgunned by Ferrari's Sebastian Vettel early on in yesterday's testing, is in need of any motivation, he was beaten into second place by Rosberg for the final three races of last season after sealing the title and expects an even tougher test from the German this year.

"Nico is going to be super quick and super strong, so I've got to make sure I raise the bar again," said the Briton.

"I've achieved it in each of the last two years - but to do it again for a third time will be tough, no doubt. That's the unknown - but I've been in the simulator recently and thankfully I can still drive, so that's a start."

Hamilton and Rosberg's relationship has been far from friendly in their three seasons as team-mates, with numerous clashes on and off the track.

And Rosberg is determined that he will finally outperform Hamilton to deliver his first world title.

"I've had the car to help me realise that dream twice now but haven't quite been able to bring everything together," he said.

"I'm looking for that key to unlocking the final step to the title all the time and I will fight for it again this year. The opposition will be strong, of course. Lewis is doing a great job and we need to keep an eye on Ferrari as well."

The man tasked with keeping the peace between Hamilton and Rosberg is Mercedes chief Toto Wolff.

Yet, he insisted they will be left to fight it out on the track, free from team orders.

"The battle between Lewis and Nico is both interesting and challenging for us", he said.

"If you put two competitive drivers in the same team and they have a shot at the championship, it's never going to be an easy ride.

"Not only do we accept that, but we also embrace it."

AGENCE FRANCE-PRESSE