AUSTIN (AFP) - Sebastian Vettel's slim hopes of stopping Lewis Hamilton from claiming a fifth world title this weekend were dented following Friday morning's (Oct 19) wet opening free practice for the United States Grand Prix when he was called to see the stewards.
The Ferrari driver was reported for a marginal speeding offence committed under red flag conditions.
Vettel may face a three-place grid penalty for Sunday's race if he is penalised in the same way as two previous drivers for the same offence this season.
Esteban Ocon of Force India and Daniel Ricciardo of Red Bull were given three-place penalties for speeding under red flags at the Japanese and Australian Grands Prix respectively.
Vettel was reported for speeding on Friday after Charles Leclerc of Sauber brought gravel back onto the circuit after a spin to create the need for red flags and a clean-up.
All drivers are expected to slow down and drive back to the pits when red flags are waved.
As heavy rain fell in the afternoon, delaying the start of the second practice session, the stewards continued with their deliberations knowing that a penalty for Vettel would damage his hopes for the race.
The German driver has to finish within eight points of Hamilton to keep the championship alive, but struggled in the wet conditions in the morning when he wound up fifth for Ferrari ahead of team-mate Kimi Raikkonen.
That left him nearly two seconds slower than Hamilton who clocked the fastest time with ease ahead of Mercedes teammate Valtteri Bottas.