Ferrari star Sebastian Vettel says any talk of a Formula One title triumph is "nonsense" at this early stage, despite his strong start to the season.

Vettel has won the opening two races of 2018 and heads to China looking to extend a streak that has already secured a 17-point lead over defending champion Lewis Hamilton at the top of the standings.

But the German faded last season after excelling early on, and he insists it is far too soon to be pondering how the campaign might end.

"I think we have so many races nowadays that it's as long, long way," Vettel told reporters at the Chinese Grand Prix.

"I think it's important, if you want to fight for the championship, to score a lot of points in every race - the more, the better - but, at this point, it's nonsense to even be thinking of where you might be. 

"Obviously there's a lot of work ahead of us. The train is leaving. Everybody is putting on new parts and improving their cars, so we need to make sure we're on that train among those teams that will still be strong at the end of the season.

"That, I think, will be key to fight for the championship."

And although Vettel got the better of Hamilton and Valtteri Bottas in Australia and Bahrain, he still considers Mercedes to be the favourites in Shanghai.

"The first two races have been quite different, so it's not that straightforward to predict the third one," he added. "I think, overall, if you take into account all the testing we did, then Mercedes is still the favourite going in.

"We'll certainly try to have a different outcome to that."