Last weekend, the FIA responded to an enquiry from Red Bull about fuel-flow sensor systems, which suggested that it was possible to pulse fuel into the engine at a higher than legal rate during the gaps between sensor measurements.

The enquiry was typical of the type made when a team believes that a rival might have such a system and wants to test the waters with the FIA.

The subsequent technical directive from Nicolas Tombazis made it clear that such an approach would be against the rules.

Ferrari had a disappointing weekend in Austin, inevitably leading to speculation that it may have been forced to respond to the technical directive and adjust the way it runs its engine.

Team boss Mattia Binotto, however, insisted the technical directive had changed "nothing" on its power unit.

The bosses of Ferrari's two main rivals both made it clear that they believe that such a system would have been a clear breach of the rules, rather than exploitation of a grey area.

"If somebody was doing what the technical directive clarified, it would have been foul play," said Wolff.

"And the way the technical directive was formulated it was a severe breach of regulations, so there is not even any talk about any grey areas."

Wolff confirmed that the numbers showed that the Ferrari package was behaving differently in Austin.

"We just had a discussion about the data from the race, and the speed trace looks very different to the last few races, whether that's down to the technical directive or down to another issue, I obviously don't know, because we can't look into what Ferrari has done."

Red Bull boss Christian Horner implied that his team and Honda would have been forced to develop such a system had it been allowed.

"The TD was very clear," said "I think that is not to say that anybody was doing anything, but if they were it would obviously be illegal.

"The power unit is an incredibly complex piece of machinery both from a hardware and software perspective, and the clarifications that we have requested were standard stuff that goes backwards and forwards continually between the teams and the FIA.

"So it is always good to get clarity before wasting effort."