Vettel was summoned the see the stewards after he was deemed not to have slowed sufficiently under red flags during a wet first practice at the Circuit of the Americas.
Stewards reviewed video evidence along with positioning data and telemetry as well as speaking to Vettel and Ferrari team representative Jock Clear before handing the German a punishment ahead of Sunday’s race.
They ruled that Vettel “did not slow sufficiently during a Red Flag period” and he “did, in fact, fail to stay above the minimum time set by the FIA ECU in marshalling sectors 6 and 7.”
Following the sodden second practice, Vettel told reporters he did slow down for the red flags.
He said: “I saw the red flag, I slowed down, I had a look around to see where the car was, [whether it was] potentially stuck in the wall or if there was one around Turn 9 and 10 and then I slowed down significantly to comply with the rules.
“They found it took too long. I think it’s pretty straightforward. Obviously I was aware, I slowed down.
“I think there should be common sense with the rules that we have… I think it’s wrong, I think I slowed down, I had a good look around at what’s going on.
“I think the rules are clear so we know but I think it’s the first time we had this in the wet and in the wet the target is a lot slower so you literally have to stop to 30kph or 40/50kph to bring down the delta. Which probably I should do next time.
“In my opinion, it’s not the right thing if there’s a car right behind you. It might run into you, but it’s more important that you don’t get the penalty.”
The penalty means Vettel will start no higher than fourth on the grid in Austin.
Mercedes man Hamilton needs to outscore Vettel by eight points to be sure of his title coronation on Sunday evening.
Vettel is currently 67 points behind Hamilton in the Drivers’ Championship with just 100 remaining from the final three races in Mexico, Brazil and Abu Dhabi.
Hamilton meanwhile, needed just one flying lap to set the fastest time in a rain-sodden second practice.
After topping the timesheets in P1, the Brit was a full second quicker than anybody else in P2 with the next fastest driver the Toro Rosso of Pierre Gasly, who finished ahead of Red Bull’s Max Verstappen.
And the mood in the Mercedes camp was buoyant at the close of the day’s rain-interrupted action.
“You know when you tell me to go steady, I am not going to,” Hamilton said over the team radio.
His engineer, Pete Bonnington, laughed: “I know. A leopard never changes its spots.”