Ferrari have rejected claims that their poor performance at the US Grand Prix was caused by a rule clarification issued over the weekend in Austin.
Red Bull's Max Verstappen said he was "not surprised" Ferrari had been off the pace following the ruling, adding: "That explains everything."
Ferrari team boss Mattia Binotto said his comments were "disappointing".
Binotto said that Ferrari had had to change "nothing at all" about their engine as a result of the FIA ruling.
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Ferrari failed to take pole position for the first time in six races and Charles Leclerc finished 52 seconds off winner Valtteri Bottas, after both drivers struggled for pace from the start of the race.
Leclerc's team-mate Sebastian Vettel retired with a suspension failure on lap eight.
The FIA document, issued on Saturday morning before qualifying, was in response to a question from Red Bull about potential ways of interfering with the mandatory fuel-flow meter that could lead it to exceed the maximum permitted fuel flow.
The document made it clear that any such intervention would be against the rules.
Some then seized on the fact that Ferrari's run of six pole positions came to an end later that day as evidence that the directive had affected them.
But Binotto pointed to the tiny gap between Sebastian Vettel and pole position winner Valtteri Bottas of Mercedes, which was 0.012 seconds and the fact that his team-mate Charles Leclerc, who was fourth on the grid, had an older-specification engine in his car following a failure in final practice.
"We were very close to pole position, as it has been in the last races," Binotto said.
"Seb could have scored the pole, he was maybe a bit too cautious in one corner, Charles had problems in morning, lost all P3 and (had) a downgrade of engine in the car. Without the issue he was potentially on the pole as well.
"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. I feel the comments are completely wrong and it is not good for the sport and everybody should be a bit more cautious."
Leclerc said of Verstappen's comments: "It's 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."
Leclerc and Vettel said their problems in the race were caused by a lack of grip, for which the team did not yet have an explanation.
Rival teams noticed a difference in the performance of the Ferrari on the straights in qualifying and race, saying its advantage had reduced compared to previous races.
Mercedes F1 team boss Toto Wolff said: "We've just had a discussions about the data from the race and the speed trace looks totally different to the last few races, whether it is down to the technical directive I obviously don't know because we can't look into what Ferrari has done."
Binotto pointed out that Ferrari had matched Mercedes in the corners and said that this was because they were running more downforce, which would affect their speed on the straights.