Red Bull say they will pull out of Formula 1 if either they cannot get a competitive engine or Audi do not join forces with the team.
Red Bull are frustrated with partner Renault's failure to master the hybrid engines introduced into F1 last year.
Motorsport adviser Helmut Marko said Red Bull were interested in doing a deal that would see Audi enter F1.
"If we don't have a competitive engine in the near future, then either Audi is coming or we are out," said Marko.
But he denied Red Bull had already been in formal talks with the German company, which is part of the Volkswagen Group.
Marko told BBC Sport: "There are so many rumours. Officially there was no request or talks. The VW Group first has to sort out who will be the new chief of support, who will run the brand of VW, and when they have sorted all these things maybe then they can think about what they are doing in motorsport.
"I was on the phone but not to the people you think."
Like all teams, Red Bull have a contractual commitment to race in F1 until 2020. They also have a contract with Renault at least until the end of the 2016 season.
Marko's remarks are a reference to a power struggle taking place at the very top of the VW Group, which also has Porsche, Lamborghini, Bugatti, Skoda and Seat among its brands.

Ferdinand Piech, who had led the German giant for more than 20 years, resigned as chairman last month.
The 78-year-old was a staunch opponent of any of VW's brands entering F1, partly because of his personal antipathy towards F1 commercial supremo Bernie Ecclestone.
Uncertainty continues to surround the senior management of Audi as a replacement for Piech has not yet been announced. His two nieces were appointed to the board to replace him and his wife, who resigned at the same time.
Senior sources in the German car industry believe Audi chairman Rupert Stadler is keen on an F1 entry, but that idea was vetoed in January by Piech.
The team had further trouble with their Renault engines at the Spanish Grand Prix last weekend.
Reliability problems mean Red Bull driver Daniel Ricciardo has already used four engines this season - which is as many as each driver is allowed to use throughout the year.
Red Bull, whose other driver Daniil Kvyat has also suffered engine failures, know it is inevitable they will be hit by grid penalties for using extra engines.
Mercedes drivers Lewis Hamilton and Nico Rosberg, by contrast, have used only one engine for all five races so far.

Marko said: "I hope the reliability issues are solved pretty soon because it is really depressing how much we are losing on the straights."
He added: "Renault see the problems themselves and we have to try and find out these problems together. It is not only reliability, it is also that we did not run most of the practice sessions because of other issues. It is also a quality problem. "

The 30-year-old has reportedly asked to keep his image rights, his trophies and his winning F1 cars, which would be very unusual given that teams tend to keep them in a trophy cabinet at their main offices.

Formula 1 bosses have agreed to bring back refuelling in 2017 as part of a range of measures aimed at making the sport more exciting.
There will also be higher revving and louder engines and changes aimed at making cars "five to six seconds a lap faster", governing body the FIA said.
For 2016, bosses have approved a plan to allow teams free choice of the four available tyre compounds for each race.
The changes still need to be approved by two further legislative stages.
The changes were agreed on Thursday at a meeting of the F1 strategy group, which comprises FIA president Jean Todt, commercial supremo Bernie Ecclestone and the Ferrari, Mercedes, McLaren, Red Bull, Williams and Force India teams. The engine manufacturers were also represented at the meeting.
The FIA statement added that a "comprehensive proposal to ensure the sustainability of the sport has emerged".
This, it said, would be refined by the teams in the coming weeks.

The engine rules, which saw the introduction of turbo hybrid engines and a fuel restriction last year, will remain stable.
This is to give clarity for any potential new manufacturers who may be considering entering the sport.
But it is the return of refuelling which will attract the most attention - the practice was last permitted in 2009.
The FIA said a "maximum race fuel allowance" would be retained. A spokesman said there had been "no agreement to change" the current 100kg limit but added: "This could evolve." However, he added that the maximum fuel-flow rate of 100kg per hour would stay.
There has been mounting criticism of the spectacle provided by F1 in recent years and the developments are a clear attempt to address that.
Drivers have been critical that the cars are too slow - in some races they are up to 10 seconds slower than in 2004.
The FIA said this would be addressed for 2017 by "aerodynamic rules evolution, wider tyres and a reduction in car weight".

The first step in improving the show will come with the freedom of tyre choices by teams next year.
Tyre supplier Pirelli said at the weekend that it had reservations about the idea but bosses have ignored this and voted it through.
They feel that providing free tyre choice will introduce variety and uncertainty into race strategy.
The FIA statement said: "All parties agreed to work together with an intention to firm up these proposals and submit them to the approval of the F1 commission and the World Motor Sport Council of the FIA as soon as possible for implementation."
A plan to allow drivers to use a fifth engine this season, one up from the current limit of four, has been rejected.