Mercedes must be 'at top of game' to secure Lewis Hamilton world title at Mexican GP, says Toto Wolff

Toto Wolff says Mercedes will need to be "at the very top of their game" to fend off Ferrari and Red Bull and secure Lewis Hamilton his fourth world championship at the Mexican GP.

Hamilton only needs a top-five finish to seal the title ahead of Sebastian Vettel and secure Mercedes their fourth consecutive Drivers' and Constructors' Championship double, after the Silver Arrows wrapped up the latter at last weekend's United States GP.

Mercedes have won both Mexican GPs since it returned to the calendar in 2015, Hamilton victorious last year having finished second to Nico Rosberg the year before.

But with the Autodromo Hermanos Rodriguez situated 2,200m above sea level, teams run their cars at high downforce and given Mercedes' struggles this season in that set-up, Wolff is expecting a stern test from Ferrari and Red Bull.

"Our target may be clear - but it will not be easy to achieve this weekend in Mexico," Wolff said.

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"This is an unusual circuit where the cars run at maximum downforce owing to the high altitude. Some of our most difficult weekends this season have come with the car running at maximum downforce, so we expect a tough and close-fought battle with both Ferrari and Red Bull.

"It will be important to be at the very top of our game if we want to get the job done."

Should Hamilton win the title on Sunday, Mercedes will become the first team to win both world championships both before and after a major regulation change.

"Although the constructors' title is now secure, we are only halfway to hitting our objectives for the season," Wolff continued.

"When we set our targets at the start of the year, it was to become the only team to win both championships across a major regulation change.

"We now have to complete that job with Lewis, who is in the best possible position with three races remaining."

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Hamilton's 66-point advantage over Vettel means the Briton can afford two DNFs and still hold a lead going into the final race in Abu Dhabi.

Vettel's championship bid imploded during the Asian flyaways - his opening lap collision in Singapore coupled with Ferrari's reliability woes in Malaysia and Japan potentially costing him 63 points - and Wolff says Mercedes will not let up their push until Hamilton secures the title.

"We know that anything can happen in this sport, and that the tables can be turned on you very quickly," he said.

"So there will be no let off in our vigilance and attention to detail in these final rounds. We will be racing to win."

See if Lewis Hamilton can clinch his fourth world championship at the Mexican GP exclusively live on Sky Sports F1. Sunday's race begins at 7pm. Want to watch but not got Sky F1? Buy a NOW TV pass from £6.99!