Red Bull's triple world champion Max Verstappen was fastest in practice for the US Formula One Grand Prix on Friday with Ferrari's Charles Leclerc second and Lewis Hamilton third for Mercedes.
Verstappen, who won the championship for the third year in a row at the previous race in Qatar, lapped Austin's undulating Circuit of the Americas in a best time of one minute 35.912 seconds on soft tyres.
Leclerc, also on softs, was 0.156 slower than the Dutch driver with seven-time world champion Hamilton third in an upgraded car and 0.281 off the pace in a sizzling hot sole practice session of the sprint weekend.
Qualifying for Sunday's grand prix was due to follow later on Friday, with Saturday dedicated to sprint shootout qualifying and the standalone 100km race.
"For sure you can see it’s bumpy and it’s working the cars pretty hard," said Red Bull team boss Christian Horner of the track conditions.
"The drivers haven’t complained about it, I think they’re just focused on where the performance limitations are and looking to find more pace."
Verstappen can take the 50th win of his career on Sunday, and record-equalling 15th of the season, if he claims his third successive victory in Austin.
Red Bull have sealed the constructors' title and have won 16 of 17 races this year.
Mexican Sergio Perez was fourth fastest for Red Bull in the session, with Haas's Kevin Magnussen fifth, also in an upgraded car, and George Russell sixth for Mercedes.
Alex Albon was seventh fastest for Williams, ahead of Ferrari's Carlos Sainz, Haas's Nico Hulkenberg and Alpine's Pierre Gasly.
McLaren's Lando Norris and Oscar Piastri, both on the podium in the last two races, did not use the soft tyres and were 15th and 19th respectively on mediums. Piastri had a scare when he ran wide at turn nine and the car snapped out of line.
Aston Martin also avoided using the softs, with Fernando Alonso 18th with a best time on hards and Lance Stroll last after getting in only five laps before being sidelined by brake problems.
Australian Daniel Ricciardo returned from injury with AlphaTauri and was 14th fastest.
