Jenson Button has insisted it is too early for him to dream of being crowned world champion even though Ferrari's Felipe Massa thinks the Briton already has the title sewn up.

Button's blistering pace in 2009 marks him out as race favourite at Sunday's Turkish Grand Prix for what would be his fourth straight win but the Brawn GP driver thinks he faces his toughest weekend to date.

Ferrari have habitually fared well at Istanbul Park - Massa has won the last three races here - and the team showed a return to their 2008 pace at the Monaco Grand Prix two weeks ago.

And Monte Carlo race winner Button warned that the Maranello outfit, as well as Red Bull and Toyota, were all capable of winning race seven of the season and putting pressure on him.

"This for me is going to be the toughest race so far this year," said Button. "There will be a hell of a lot of good fights out front for the duration of the weekend. We'll have a car that's competitive and capable of winning once again but so will Ferrari, Red Bull, Toyota and maybe even McLaren.

"People keep on talking about the championship but we're just six races in so it's not even a consideration and, even if I win in Turkey, there's a long old slog left. All I'm focusing on is trying to make it four wins in a row. It's got a nice ring to it, hasn't it?"

Button is bidding to become Britain's 10th Formula One world champion but he warned: "I've got a job to do before I can even think about something like that. Getting in the record books is a nice idea but it's not something you think about. Hopefully I can look back and enjoy it all at the end of the season but there are so many challenges and so many more laps of racing to contend with before then."

The Brawn racer has a commanding lead in the championship - he lies 16 points clear of team-mate Rubens Barrichello and a further 12 clear of Red Bull racer Sebastian Vettel.

Massa, who last year finished just a point behind champion Lewis Hamilton, is already 43 adrift of Button and is convinced the 29-year-old will end the campaign as No1.

"I'm not the kind of guy who gives up very easily, so I'll fight until the last corner of the last race," said Massa (below), who this week played in a football match between F1 drivers and a Turkish All-Star XI in Istanbul.

"But in my experience, Brawn will be champions. It's impossible to believe they are going to lose the championship. For me it's already over.

"They have a really competitive car with which it is easy to score points, so even if we win as many races as possible, they are going to be there."

Brawn, meanwhile, have made it clear they plan to offer Button a lucrative new contract as a reward for his form this season and in a bid to fend off interest from rival teams for the championship favourite.

The Briton dismissed talk of the future and insisted his sole focus was on 2009. "We're only six races into the season and I've put six years of my life into this team," he said. "Now is not the right time to talk about contracts. I'm very happy where I am.

"The most important thing is for me and the team to be competitive this weekend and I believe we will be."