Sebastian Vettel has responded to allegations from Red Bull’s Max Verstappen surrounding Ferrari’s Formula 1 engine by calling the comments “not professional” and “not mature”.

Intrigue has surrounded Ferrari’s engine after it experienced a dip in straight-line speed performance over the United States Grand Prix weekend, coinciding with a technical directive being issued over fuel flow systems by the FIA.

Charles Leclerc finished the race over 50 seconds behind race winner Valtteri Bottas, while Vettel retired early after slipping from second to seventh on the opening lap.

Verstappen was outspoken about Ferrari’s fall in performance, saying it was “not strange” and used the word "cheating" on Dutch TV, prompting an angry response from Ferrari chief Mattia Binotto and Charles Leclerc.

Vettel declined the respond to Verstappen’s comments in Austin two weeks ago, but said on Thursday at Interlagos it was “a sign of our times that a lot of people have something to say.”

“Everybody is free to say what they want if that’s what he thinks, that’s what he might think. But obviously we have a different opinion,” Vettel added.

“Should we have the strongest engine - I don’t know the other manufacturers' power figures - that’s a great achievement by us, by our engine department. For the last five years, we had Mercedes having the strongest engine.

“But since now for a couple of months we are ahead, then hopefully it stays like that for the next five years and I don’t care what people think or say.”

Asked to expand on his response to Verstappen, Vettel said: “I don’t think anybody in the team took it personally.

“I think it’s not professional and not mature, but I can also see that you are probably interested in me answering back. I don’t have much interest in that, other than saying that for us, the best way to answer in a way is to probably go back to normal.

“We are not proud of how we performed in Austin on Sunday. After Saturday, nobody had the need to complain. On Sunday, I think we struggled probably with more than one thing, conditions, tyres, setup, which are things we need to work on.

“Calling it that far [cheating] I think is not right. But again, live and let live. If that’s what he thinks, that’s what he thinks. If next week he thinks something different, then, in the end, we don’t care so much.”

Additional reporting by Julianne Cerasoli.