Lewis Hamilton is refusing to take his healthy championship lead for granted, insisting he does not feel he has one hand already on the 2018 Formula 1 title.

Hamilton extended his advantage over chief title rival Sebastian Vettel thanks to victory last time out in Singapore, which saw him move 40 points clear with 150 up for grabs in the remaining six races of the season.

But speaking ahead of this weekend's Russian Grand Prix, the Briton dismissed suggestions the final destination of this year’s drivers’ championship is already a foregone conclusion and said he will keep focused in his bid to beat Vettel to a fifth world title.

COTA #1 - Hamilton Vs Vettel

"I don't think you ever have one hand on it," Hamilton replied when asked if he felt he has one hand on the 2018 drivers’ title.

"You either have both hands on it, or you don't. Same as the last race, just taking it one race at a time, there's still a long way to go, a lot of points available.

"Six races are still a lot of races, it's a long season. We're really just head down, everyone's working incredibly hard to continue to improve the car.

"We're going to be faced with different challenges as we come to these different races, so the job is still exactly the same. The target is still exactly the same and the approach is still exactly the same."

Hamilton, who said in Singapore he is already pushing Mercedes to bring forward 2019 developments to the final race of the season in Abu Dhabi, stressed he continues to push his engineers for improvements and reckons the German manufacturer is better positioned heading into this year’s race in Sochi compared to 2017.

"I'm a pain in the ass to my engineers upstairs. I'm always challenging, challenging, challenging. Even if I'm wrong, still questioning, questioning, questioning,” he explained.

"Some of that, I like to think, has had a positive impact... to spring an idea or a direction in which we've pushed the car and our understanding, for example of the tyres.

"I really do believe this weekend we'll be in a better position than we were here last year. Our understanding of the tyres is far greater than it was when we arrived here last year.

"It's still a challenge to get right. So, we will take our understanding from last year and that experience with a pinch of salt because the car is different, it's improved, and we've got different tyre this weekend."