Wolff: Hamilton 'on another level' since summer break

Mercedes Formula 1 boss Toto Wolff says Lewis Hamilton has been "on another level" since returning from the summer break as he closes in on a fourth drivers' world championship.

Hamilton can wrap up the title in this weekend's United States Grand Prix by pulling a further 16 points clear of Ferrari rival Sebastian Vettel, having forged a 59-point advantage with four wins and one second-place finish since the summer break.

Mercedes looks likely to clinch its fourth straight constructors' championship in Austin this weekend, with Wolff putting the team's success down to its constant push for improvement, never resting on its laurels.

"We have maintained clear sight of the reasons for our success this year. The team is operating at an incredibly high level in every area and continuing to develop," Wolff said.

"We have applied an obsessive attention to detail to how we go racing over the past three seasons, and we have continued to develop our car at a competitive rate through the season.

"Our mindset has always been one of constant improvement, regardless of the results we were enjoying, and this is now paying off."

Wolff hailed the strength of Hamilton and teammate Valtteri Bottas in lifting the team, making particular mention of the champion-in-waiting's recent form.

"Lewis has driven brilliantly this year, and since the summer break in particular, he has been on another level," Wolff said.

"It has been impressive to watch him extracting everything from the car and working with the team to solve problems and improve even further.

"Valtteri has had a tougher time in recent races - but he demonstrated his work ethic and character to deliver a strong weekend in Suzuka, and he will be aiming to build on this performance in the final four rounds."