Formula 1: Mercedes boss Toto Wolff says big championship lead is 'no comfort'

Mercedes say they take "no comfort" from Lewis Hamilton's 40-point lead over title rival Sebastian Vettel heading into the Russian Grand Prix.

Hamilton has won three of the past four races while a string of mishaps have left Ferrari and Vettel trailing with six races and 150 points remaining.

"It is better to have a lead than not, but there are plenty of points to score," said Mercedes boss Toto Wolff.

"There is no naive optimism about our situation with the team."

Wolff said Mercedes were "excited for the fight we will certainly have in the next six races" and insisted they would "continue to concentrate on every single session, trying to optimise the car in every possible area - and we will go for the race win".

And he played down the importance of the fact that Mercedes have won all four races so far held on the Sochi Autodrom around the Black Sea resort's Olympic Park.

"We have a good track record in Sochi but we know that Ferrari and Red Bull will give it everything to break our winning streak, so we must fight as hard as ever to make are we bring home as many points as possible."

The Russian race has been moved back to its original autumn slot, after two events held in the spring.

"With the race being held in September, we're going back to weather conditions that will be similar to those of 2014 and 2015, when the Russian Grand Prix took place in early October," Wolff said. "We don't have any data from the current regulation cars in those conditions in Sochi, so this adds another challenge to the race."

Wolff also backed Mercedes' second driver Valtteri Bottas, who admitted at the last race in Singapore that he was finding it "hard" up against Hamilton amid the realisation that he was now out of the title fight this year.

The Finn took his maiden victory in Russia last year and Wolff said: "For every racing driver, that's a very difficult situation to be in because everything you dream about and everything you work for is winning the world championship.

"When you realise you're not in the hunt any more, that's very difficult to handle.

"But Valtteri has shown that he has the speed, the talent and the work ethic to win in a Mercedes.

"He has always been a team player and that is one of his greatest character traits.

"Valtteri could have won races this year, but the odds were against him. However luck isn't just a one-way street; and I know that Valtteri has every ingredient it needs to win at this level. He just needs to keep working hard to improve and trust that the tables will turn for him."