The US Grand Prix stewards have handed a 3-place grid penalty to Sebastian Vettel for failing to slow down sufficiently under red-flag conditions in FP1.
The punishment will only further complicate the Ferrari driver's task on Sunday, with Lewis Hamilton needing to outscore his title rival by just 8 points to clinch his fifth world crown.
The specific incident for which Vettel has been punished took place in the morning session when the red flag was brought out following a spin by Sauber's Charles Leclerc that brought gravel out on the track.
The stewards' sanction, justified by Vettel's failure to slow down sufficiently during the red flag period, was expected following a similar incident involving Force India's Esteban Ocon in Japan.
The stewards labeled the offense an "extremely serious matter", insisting the applied penalty was "consistent with previous rulings".
If Hamilton wins on Sunday, Vettel will require a second-place finish to remain in contention for the championship.
"I think I saw the red flag, I slowed down, had a look around [to see] where was the car potentially stuck in the wall, if there was one around Turn 9 and 10 and then slowed down significantly to comply with the rules," explained a resigned Vettel.
"They found it took too long.
"I think it’s the first time we had [the target lap] in the wet and in the wet the target is a lot slower, so literally I have to stop to 30kph or 40, 50 kph, to bring down the delta, which probably I should do next time.
"In my opinion it’s not the right thing, [because] if there’s a car behind you, it might run into you, but more important that you don’t get a penalty."