Max Verstappen set the ultimate pace in United States Grand Prix final Formula 1 practice, holding a healthy 0.320s advantage over Charles Leclerc.
Verstappen became the first driver this weekend to set a time below the 1:36 mark, posting a 1:35.825s effort on the Soft tyres to cement his pace advantage heading into Saturday's qualifying session.
Charles Leclerc led a Ferrari 2-3, but the Monegasque will take grid penalties, ruling him out of claiming Pole Position.
Sergio Perez and Lewis Hamilton rounded out the top five positions.
Verstappen and Leclerc duelling for top spot
In the early stages of the final 60-minute practice, Verstappen vaulted to the top of the timing screens with a time of 1:36.706s, enjoying an advantage of about one tenth of a second to teammate Perez.
The Mexican then responded to pump in a 1:36.578s to enjoy a brief period in P1 as the field began preparations for their final qualifying simulation runs.
Verstappen then traded lap times with the penalised Leclerc, originally posting a 1:36.223s, with Leclerc just 0.010s behind on what he called a "very messy" lap.
Sainz was just 0.048s behind at this stage, although Verstappen's 1:35.825s on his final flying lap on a new set of Softs cemented him in P1 - with Leclerc only managing 1:36.145s.
The second Ferrari ended 0.446s down, with Perez pipping Hamilton at the death to fourth. The seven-time champion showed a decent turn of speed, although he abandoned a lap after a lairy moment at Turn 19.
Hamilton was the last driver within one second of Verstappen's benchmark.
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Alonso best of the rest
Alpine's Fernando Alonso - who is also taking a grid drop - was sixth, one tenth ahead of George Russell in the second Mercedes.
Aston Martin continued their strong weekend: Both Sebastian Vettel and Lance Stroll were firmly inside the top 10, around 1.3s slower than Verstappen, with AlphaTauri's Pierre Gasly rounding out the top 10.
Valtteri Bottas was 11th for Alfa Romeo, with Lando Norris 12th on a quiet weekend for McLaren.
Esteban Ocon was out-paced by Alonso by nearly half-a-second in 13th, with Haas' Kevin Magnussen and a brake-problem hit Daniel Ricciardo 15th.
Technical problems for Schumacher
Mick Schumacher endured a tricky session with a gearbox problem costing him nearly half the session after completing nearly a full lap at reduced speed.
He emerged late on but could only go 19th quickest, about seven-tenths and five places behind Magnussen.
The second AlphaTauri of Yuki Tsunoda was 16th ahead of the Williams duo of Alex Albon and Nicholas Latifi, who were separated by 0.124s.
20th and last was Zhou Guanyu, whose Alfa Romeo had a problem and was 3.910s down on Verstappen.
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RacingNews365.com F1 journalists Dieter Rencken and Michael Butterworth discuss the key issues from the Japanese Grand Prix, including Max Verstappen's dominant run to his second World Championship, and whether F1's current system of awarding points in shortened races needs tweaking.