Ferrari's Charles Leclerc led Mercedes' Kimi Antonelli in Friday practice at the United States Grand Prix - but Max Verstappen left the strongest impression in his Red Bull.

Leclerc, who topped both sessions, was 0.042 seconds ahead of the Italian, who has a mathematical chance of tying up his first world title this weekend.

Antonelli will win the championship in Austin only if he wins the race and team-mate George Russell finishes below eighth and Ferrari's Lewis Hamilton below fourth.

Verstappen was third fastest, 0.189secs back, ahead of Hamilton, although the seven-time champion was 0.615secs off the pace. Russell was fifth ahead of Racing Bulls' Liam Lawson.

Verstappen appeared fastest on the race-simulation runs later in the session, which often provide a more accurate read of overall competitiveness than the single laps.

The Dutchman could be compared directly only with the Ferrari drivers, as all were running the soft-compound tyres on their long runs.

Verstappen was marginally faster than Leclerc on average but the consistency of his pace suggested he was in the best shape, at least on Friday.

Hamilton appeared to be struggling for pace compared with Leclerc whether on short runs or long.

Ferrari have an upgrade on their car this weekend, focused on a new floor, but Leclerc was downplaying expectations.

"It felt good but it is not the gain I have seen or heard about," Leclerc said. "It is small gains but we could still see them on the car. It is a small step forward and we started the weekend on the right foot with a good balance and that is the outstanding thing with this Friday.

"It has been a very clean Friday for me, but the others seem to be gaining more than us from Friday to Saturday and seeing the little gap there is, it is not going to be so easy tomorrow."

Leclerc picked up on Verstappen's complaints about the track surface on Thursday by saying: "It was very poor. The first sector is particularly poor and very bumpy."

McLaren's Lando Norris was seventh fastest, although the world champion did not set a time on his qualifying simulation run on soft tyres after making a mistake at Turn 16.

Norris was the fastest on the long runs, at about 0.2secs on average faster than Verstappen, but cannot be compared as he was running the hard tyre.

McLaren have introduced the first of three consecutive planned upgrades this weekend, but he was not happy with his performance.

"Difficult," Norris said. "The pace is not bad. We seem a step away from Red Bull and Ferrari, probably Mercedes as well, but the car is very difficult to drive, too difficult to be consistent and get a nice feeling consistently.

"To get the car be quick we just have to try so hard to be perfect and you can't be perfect. I am sure everyone has similar problems in a way but we are just not quick enough yet to be there consistently enough."

McLaren's Oscar Piastri was eighth quickest, ahead of Red Bull's Isack Hadjar and Haas driver Oliver Bearman.

Mercedes have reverted both their cars to the upgraded specification that was introduced in Malaysia two races ago but about which there remain questions over its relative performance.

The team believe that the upgrade has more performance within it, but that they have not yet found the appropriate set-up to maximise it. They hope a full, 'normal' weekend with three practice sessions will enable them to hone it.

"Having both cars on the same package helps because we can try lots of different stuff and we have a better understanding of this package," Antonelli said.

"However, we are still trying to get the car in the right window."

Three drivers have grid penalties for using more than the permitted number of engine parts - Racing Bulls' Arvid Lindblad will go back five places, Audi's Gabriel Bortoleto 20 and Alpine's Franco Colapinto 10.