By Alan Baldwin
LONDON (Reuters) - Four-times Formula One world champion Lewis Hamilton has yet to sign a new contract with Mercedes but talks are going well, team principal Toto Wolff said on Thursday.
"Lewis has become such an important pillar within the team that it's a no-brainer that we continue with each other," the Austrian said in an interview on the team website (www.mercedesamgf1.com).
"The discussions are ongoing in a very positive mindset and it's just a matter of time when we seal it and put a signature to the document."
Hamilton, 33, is out of contract at the end of 2018 -- a year that could see him become only the third driver to take five championships after seven-times title winner Michael Schumacher and the late Argentine Juan Manuel Fangio.
The Briton said in November that he expected negotiations to be straightforward.
"It is quite an easy process for us," Hamilton said then. "We already have something in place and it's really just about extending it and enhancing it, working on what more I can do for them, for the sponsors, the brand and vice versa."
Since then, Hamilton has erased much of his social media and kept a low profile.
His Twitter feed, followed by 5.25 million people, now has only two posts -- one from the team and the other a sponsor -- that the driver has retweeted.
The season starts in Australia on March 25.
Wolff said the new F1 W09 car, to be launched at Silverstone on Feb. 22, was being fired up at the factory for the first time on Thursday.
"We've had a good winter, I would say," he added. "No real drama, but there is always stress within the organisation at that time of the year."
Last year's car was described by Wolff as a bit of a 'diva' for its handling characteristics and the Austrian said testing at the end of the month would show whether the new one was better behaved.
(Reporting by Alan Baldwin, editing by Christian Radnedge)