Red Bull team principal Christian Horner has warned Audi it should not underestimate the scale of the challenge it faces when joining the F1 grid in 2026.
Audi confirmed ahead of the Belgian Grand Prix in August that it will enter F1 as a power unit supplier when the new engine regulations are introduced.
Given Red Bull has recently built the first prototype power unit at its new powertrains facility in Milton Keynes, Horner is well placed to advise Audi on the trials it can expect over the coming years.
"You absolutely shouldn't underestimate the scale of the challenge," said Horner.
"It's massive when you look at the current incumbents that we're competing against, the longevity, the continuity that they've had.
"Of course, a company like Audi's reputation talks for itself. But the scale and the size of the challenge, as we've seen ourselves at Red Bull, is enormous, especially when you're starting from scratch."
FIA delay key to Red Bull and Audi
The new power unit regulations were originally set to be introduced in 2025 only to be delayed by a year.
Even with over three years to prepare, however, Horner conceded it will be a tight battle to be ready on time.
"It's exciting, because it is a challenge and you have to believe anything is possible," added Horner.
"Of course, the regulations are a key aspect to that. Thankfully they were delayed 12 months to 2026, otherwise, I don't think you would have seen either potentially Red Bull or Audi participating in the sport.
"But even 2026...it's 10 past midnight and Cinderella's already buggered off.
"So, it's tight, but that's Formula 1 and that's some of the creativeness and drive that happens within the teams.
"It's going to be exciting to see more power unit manufacturers on the grid for 2026."