Lewis Hamilton went a full second quicker than his rivals with his only push lap in wet conditions at the Circuit of the Americans on Friday afternoon.
Persistent heavy rain meant that no-one took to the circuit until over halfway through the 90-minute second practice session.
Full Wet tyres were initially used, with Intermediates fitted for the final 20 minutes, though the green-banded rubber was the quicker option for only the last 10 minutes, as conditions gradually improved.
Hamilton remained in the garage for much of the session and emerged for just one push lap, which was a 1:48.716.
That left him a second clear of Toro Rosso’s Pierre Gasly, with Red Bull’s Max Verstappen third.
Fernando Alonso put McLaren fourth with his only push lap, ahead of Renault’s Nico Hulkenberg and Toro Rosso’s Brendon Hartley, whose 19 laps left him as comfortably the most productive driver.
Marcus Ericsson and Stoffel Vandoorne were seventh and eighth respectively for Sauber and McLaren, as Ferrari pair Kimi Raikkonen and Sebastian Vettel capped the top 10.
Vettel’s best effort was 5.2s adrift of Hamilton’s benchmark.
The Ferrari driver's title prospects have taken a further blow with the news that he has been handed a grid penalty for a red flag transgression in FP1.
Only five other drivers recorded a timed effort while four – including Hamilton’s Mercedes team-mate Valtteri Bottas and Red Bull’s Daniel Ricciardo – did not take to the circuit.
Saturday’s one-hour third practice session is scheduled for 13:00 local time
