Lewis Hamilton is firmly in the driving seat to win a historic fifth world championship at Sunday’s US Grand Prix after his rival Sebastian Vettel was hit with a grid penalty.

The Ferrari driver will be pushed back three places after he was deemed guilty of failing to slow sufficiently under red flags during opening practice on Friday.

If Hamilton takes the chequered flag, and Vettel, who can now start the race from no higher than fourth, fails to finish runner-up, the Briton will wrap up the title with three rounds remaining.

Vettel, whose championship challenge has been plagued by a series of mistakes, was summoned to the stewards following the incident in the first running of the day here at a rain-sodden Circuit of the Americas.

The session was temporarily suspended with gravel on the track following a spin by the Sauber of Charles Leclerc.

Vettel took too long to react to the red flags and, in addition to his costly grid penalty, the German was also slapped with two points on his licence.

“There should be common sense with the rules we have,” he protested afterwards. “The stewards were very specific. They said I took 27.7 seconds to slow down. I saw the red flag. I slowed down, and they found that it took me too long.

“It is the first time we have had this ruling in the wet and you literally have to stop 30 or 40 kilometres per hour which I should do next time.

“In my opinion it’s not the right thing to do as the car behind might run into you.”

Hamilton, who was fastest in both practice sessions in Austin, needs to outscore Vettel by just eight points to win the championship, and emulate Juan Manuel Fangio with a quintet of titles.

The Englishman needed just one flying lap to set the fastest time in second practice.

Offered the choice between remaining in his Mercedes garage or risking the elements on track, the championship leader told his team he was ready to go.

As in the opening running, it was Hamilton’s name which finished at the top of the time sheets.

Hamilton was a full second quicker than anybody else with the next fastest driver the Toro Rosso of Pierre Gasly, who finished ahead of Red Bull’s Max Verstappen.