Austin (AFP) - Red Bull’s world champion Max Verstappen was fastest in Saturday’s gusty third and final free practice session for the United States Grand Prix, the Dutchman beating Ferrari’s Charles Leclerc by 0.320 seconds.

Verstappen clocked a best lap in one minute and 35.825 seconds in the final minute of a closely-contested session that saw both Ferraris and both Red Bulls promising race-winning pace.

Carlos Sainz was third for Ferrari ahead of Sergio Perez in the second Red Bull and seven-time champion Lewis Hamilton of Mercedes.

Hamilton will look to take advantage of both Leclerc and Perez in qualifying as both face grid penalties for taking new power unit components.

On another near-perfect, if breezy, day at the Circuit of the Americas, with an air temperature of 29 degrees and the track at 39, Leclerc and Verstappen were quickly setting the pace as the teams focused in earnest on lap times after Friday’s tyre testing.

Ferrari had topped both sessions on the opening day, Sainz in the morning and Leclerc later in the day, but it was more notable for the windy conditions and some of Hamilton’s comments about the bumpy nature of the track.

“Horrible,” said the seven-time champion when asked how it felt to drive the circuit again, having won five times in Austin. “I came here after Montreal and I drove last year’s car and, oh, it was so good. I remember getting out just beaming from ear to ear. It was so smooth, good downforce, good power.

“This year, we lost a bit of power with the biofuels and the car is so stiff and now you come and drive this car…. Luckily, I don’t have many fillings because, if I did, they would have all come out for sure. It’s just so bumpy!”

On Saturday, the Briton had less to grumble about - after Perez went top 14 minutes into the session, he responded with conviction and was briefly on top before a final flurry of faster times by his rivals.

Perez came back as Red Bull, battling to defend their reputation after being charged with exceeding the sport’s cost cap last year, regained the ascendancy with Verstappen taking over on top in 1:36.223 with eight minutes remaining – and Leclerc responding only 0.01 seconds off the champion’s pace.

Both drivers were enjoying throwing their cars around and Verstappen was warned by his team. “You’re maybe pushing the braking zone too hard into Turn One,” they told him on team radio.

“A very messy lap,” admitted Leclerc who, along with Alonso, Perez and Zhou Guanyu of Alfa Romeo will be facing a grid penalty having taken new power unit parts for this weekend’s race.

In the final seconds, Leclerc went top in 1:36.145 only for Verstappen to beat him with 1:35.825, taking the leading position from his Monegasque rival as he bids to clinch Red Bull’s first constructors’ championship triumph since 2013 on Sunday.

Two-time champion Fernando Alonso of Alpine was sixth ahead of George Russell of Mercedes, four-time champion Sebastian Vettel and his Aston Martin team-mate Lance Stroll and Pierre Gasly of Alpha Tauri.