17:34 – Mercedes’ Lewis Hamilton set the quickest time during the opening 90-minute session at a drizzly Circuit of the Americas, ahead of title rival Sebastian Vettel and team-mate Valtteri Bottas.
Light rain prior to the start of the session left the circuit damp, and drivers took to the track on Intermediates, with some using the 2017-spec rubber, and others trialling Pirelli’s prototype compound.
Red Bull’s Max Verstappen led the way before conditions improved approaching the mid-point of the session, enabling Vettel to switch to Super Softs.
Vettel, despite a tardy final sector, edged clear, though was demoted by Daniel Ricciardo after a brief mid-session lull, as the Australian put his Red Bull on top.