Ferrari's Charles Leclerc led Mercedes' Kimi Antonelli in Friday practice at the United States Grand Prix.

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.

Red Bull's Max Verstappen was third fastest, 0.189secs back, ahead of Ferrari's Lewis Hamilton, although the seven-time champion was 0.615secs off the pace.

Mercedes driver George Russell was fifth ahead of Racing Bulls' Liam Lawson.

McLaren's Lando Norris, whose team have introduced the first of three consecutive planned upgrades this weekend, 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.

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

Antonelli will win the championship in Austin only if he wins the race and Russell finishes below eighth and Hamilton below fourth.

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.

Ferrari have an upgrade here which is fundamentally a new floor. Both Leclerc and Hamilton played down its potential impact.

Hamilton said: "We have a very, very small upgrade this weekend. It's less than a tenth. It's like half a tenth.

"So, I don't think that propels us forward enough to necessarily challenge that deficit. But maybe the track suits our car, and maybe they'll have a one-off weekend. Maybe Mercedes will have an off weekend again, and we'll be right there to take it."