Lewis Hamilton leads Sebastian Vettel in final US GP practice
Mercedes' Lewis Hamilton underlined his domination of the United States Grand Prix weekend with fastest time in final practice on Saturday.
It completes a clean sweep of practice sessions for the championship leader, who was 0.092 seconds quicker than title rival Sebastian Vettel's Ferrari.
Hamilton will clinch his fourth world title if he wins the race on Sunday and Vettel finishes lower than fifth.
Hamilton's team-mate Valtteri Bottas was third and Kimi Raikkonen fourth.
Although Vettel was slower than Hamilton, the session marked a major step forward for Ferrari after a terrible day for the German on Friday.
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Vettel had a spin, was half a second slower than Hamilton and then did no race-simulation work on Friday afternoon, and Ferrari changed his chassis ahead of final practice after being unable to find a problem that he said made the front axle "feel like jelly".
But Saturday morning brought a revived Ferrari, Vettel and team-mate Raikkonen competitive from the outset.
In the end, there was about 0.1secs between each of the drivers in the top four, and 0.277secs covered the Mercedes and Ferrari drivers.
Red Bull's Max Verstappen was fifth quickest, but 0.739secs off the pace and facing a 15-place grid penalty for using too many engine parts.
Carlos Sainz continued his impressive debut for the Renault team, just 0.042secs off team-mate Nico Hulkenberg as the pair took seventh and eighth places behind the Williams of Felipe Massa.
Red Bull's Daniel Ricciardo was struggling in ninth place, 0.6secs off Verstappen after a wayward fastest lap, and ahead of the Force Indias of Sergio Perez and Esteban Ocon.
Massa's team-mate Lance Stroll was 12th, ahead of the McLarens of Fernando Alonso and Stoffel Vandoorne, the Spaniard complaining that his set-up "didn't work".
New Zealander Brendon Hartley ended the session 15th for Toro Rosso on his F1 debut, but there was no benchmark for him because Daniil Kvyat suffered a technical problem and could manage only six laps.
Unusually, there are four hours before qualifying at 22:00 BST (16:00 local) as the schedule is changed in the hope more people at the track will attend the Justin Timberlake concert in the evening.