Australia's Formula One star Oscar Piastri has started the Las Vegas Grand Prix well off the pace, as McLaren teammate Lando Norris took the early honours before a red flag ended practice early.
Championship leader Norris clocked a lap time of 1:33.602 seconds to go fastest in the second red-flagged practice session on Friday (AEDT), while Piastri was 14th.
Mercedes rookie Kimi Antonelli trailed Norris by 0.029 seconds, with Ferrari driver Charles Leclerc third-fastest before suffering a gearbox issue with less than four minutes on the clock.
Red Bull's four-time world champion Max Verstappen finished Friday in ninth.
Norris, who leads Piastri in the standings by 24 points, had aborted his first lap as he adjusted to a newly trimmed rear wing before surging up the order.
Piastri's bid to improve his time of 1:34.493 in the one-hour session was derailed when concerns over a possible loose drain cover between turns 16 and 17 brought out the first red flag.
First enduring a 20-minute delay, drivers had less than seven minutes before another red flag for track maintenance prematurely ended the session.
Preparing for the third-last round of the championship, contender Piastri will have little margin for error in Las Vegas - a track that has not favoured McLaren in the past.
The 24-year-old Melburnian had led by 34 points just over 10 weeks ago, but now finds himself behind Norris after an alarming slump in which he's failed to make the podium in his last five races.
Verstappen remains in contention as well, 49 points behind Norris.
Leclerc had set the pace in the opening practice session on Friday, lapping the floodlit track with a best time of 1:34.802 seconds.
The Ferrari driver went 0.166 seconds quicker than Williams rival Alex Albon, followed by Red Bull pair Yuki Tsunoda and Verstappen in third and fourth, respectively.
with PA, Reuters
