AUSTIN, TEXAS (REUTERS/AFP) - Ferrari have responded angrily after Red Bull driver Max Verstappen suggested the Italian team's poor performance at the United States Grand Prix was linked to Formula One's governing body closing a potential engine loophole.
Ferrari had racked up six straight pole positions, and shown impressive straight-line speed, before Mercedes were back on top in the race in Austin with Valtteri Bottas winning from the front of the grid.
Ferrari were off the pace on Sunday (Nov 3), while Bottas led team-mate Lewis Hamilton, who clinched his sixth world title, in a one-two with Verstappen third.
F1's governing body issued a technical directive before the race in response to a Red Bull query, ruling out a sophisticated way of increasing the fuel flow to boost performance.
Asked afterwards in a news conference whether he was surprised by Ferrari's lack of performance and could offer an explanation, third-placed Verstappen suggested they had been bending the rules.
"Not surprised, at all, about it. After what came out. So that explains everything," replied the Dutch 22-year-old. In a separate interview with Dutch television, he used the word "cheating".
Ferrari team principal Mattia Binotto said he was disappointed by the comments.
He pointed out that Sebastian Vettel had missed pole by a mere 0.012sec and that Charles Leclerc raced with an old engine after problems in final practice.
"If we look at the race, certainly the speed on the straight was not our issue and we had clear problems with grip on the car on the first stint on both drivers," Binotto told reporters.
"I feel the comments are completely wrong and it is not good for the sport and everybody should be a bit more cautious," added the Italian.
He had said earlier in the week that Ferrari's engine was completely legal and the team were annoyed by continuing paddock rumours.
Leclerc, who finished fourth, 52sec behind Bottas, said Verstappen's comments were "a joke".
"He has no clue. He is not in the team. I don't know why he is speaking, he doesn't know anything about us," said the Monegasque.
Vettel retired after eight laps of the race with rear suspension failure. He said he had no explanation for his car's breakdown.
"I had a decent start, I was just on the dirty side - and then I had no place to go at Turn One," said the German.
"I was really struggling for grip, especially at right-handers. It was a very different car, so I asked if they had seen something or if something is broken.
"A couple of laps after that we had the failure. I assume that it must have been an issue before. I don't know if it's related to the track, but on the other hand we've done so many laps. Why now, and not Friday?"
Leclerc said the front left tyre of his car felt "very, very weird" in the first stint.
"I was not expecting that," he said. "It did not seem right.
"The first stint was extremely hard and I believe this was the main problem of the race, but to be completely honest I have no explanation... We need to analyse that because I've never had this feeling before. I'm pretty sure something was not right on this stint.
"Then on the two others the pace was not as bad."