Red Bull motorsport advisor Helmut Marko has said that the team will pull out of the sport if they don't return to the front of the grid in the near future.
The Austrian team has struggled since new technical rules were introduced at the beginning of 2014, and they appear to have taken a major step back this season.
Audi has been heavily linked with F1 in the pass, and reports suggest that they are considering a possible deal with the former champions.
Marko told BBC Sport: "If we don't have a competitive engine in the near future, then either Audi is coming or we are out."
Red Bull has a contract to race in F1 until 2020.
