Red Bull team principal Christian Horner has confirmed that the introduction of the upgraded Renault engine has been pushed back due to reliability concerns.
The French manufacturer revealed in the build-up to the United States Grand Prix that they have used 11 of their 12 in-season development tokens and the upgraded engine would be available for use by Red Bull in Texas.
However, after holding discussions with the Milton Keynes-based team, it was decided not to introduce the power unit in Austin with Daniel Ricciardo claiming it is "probably not worth taking" any risks, especially as it would have resulted in grid penalties for both Red Bull drivers.
Horner also admitted during FP2 in Texas that the new-spec engine will probably only be used at the penultimate race of the season at Interlagos in Brazil as Renault still needs to do more running as they have concerns about reliability.
Renault's director of operations Remi Taffin added to Motorsport.com: "We are not going to use it for some good reasons: which are overall, we decided it was not the best way to achieve the weekend and to get the most out of it.
"First because if you look at this weekend, taking the ten places penalty versus what we would have gained, seems to not be worth it.
"And if you look also at the conditions when it is wet, the Red Bull Renault is much better in these conditions – so it is even worse if you take a 10-place penalty.
"Then, if you look at the opposition, some have decided to take some penalties so all in all we are happy not to take that engine for that weekend."