Mercedes driver George Russell led the standings in a caution-filled third and final practice for the Las Vegas Grand Prix ahead of qualifying later on Friday.
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In damp, greasy conditions, Britain's Russell saved his best lap for last, clocking a time of one minute 34.054 seconds to pip reigning Formula One world champion Max Verstappen of Red Bull by 0.227secs.
Alex Albon for Williams was third quickest in 1:34.875, ahead of Racing Bulls' French driver Isack Hadjar in fourth and Ferrari's Lewis Hamilton fifth.
But it was an unspectacular session for championship leaders Lando Norris and Oscar Piastri, who both appeared to be adopting a safety-first approach in awkward conditions ahead of qualifying later in the evening.
The McLaren duo, who are battling for the drivers title, finished bottom of the timings, with championship leader Norris 3.058sec behind Russell's time in 1:37.112.
Australia's Piastri was only marginally faster, finishing 19th quickest with a time of 1:37.023.
Norris is aiming to tighten his grip on the championship this weekend after back-to-back wins that have left him eyeing a maiden title.
The Briton boasts a 24-point lead in the drivers' standings over Australian teammate Piastri heading into the Vegas race after a remarkable turnaround in form.
Australian Piastri, who was 34 points clear after winning the Dutch Grand Prix on August 31, has failed even to post a podium finish in the past five races.
Norris has found consistency at the right time, following up his victory from pole position in Mexico with a sprint success and another race win from the front of the grid in Sao Paulo last time out.