Red Bull adviser Helmut Marko says the team has already decided it will quit Formula One if it cannot secure a competitive engine to replace Renault for 2016.
Red Bull is moving closer to an early divorce from engine supplier Renault following the breakdown of its relationship this season. Mercedes has already ruled out a customer engine deal for Red Bull, fearing the consequences of equipping a rival with a dominant power unit, while Honda is both struggling and fully committed to McLaren.
That leaves Ferrari, who supplied Red Bull in 2006 and junior team Toro Rosso between 2007 and 2013. The Italian company has said it would not be "scared" of supplying Red Bull but a deal is unlikely until the Milton Keynes outfit confirms its split from Renault.
Red Bull threatened to quit earlier this year over F1's current engine regulations, and Marko says the team will not accept an uncompetitive engine next year.
"The decision is done, if we don't have a competitive engine we will leave Formula One," Marko told Sky Sports News, speaking after Red Bull driver Daniil Kvyat topped FP2 under the lights in Singapore."Today we are ahead, but maybe that will change tomorrow, but we will be very near the front. As long as you don't have a power unit that which can compete it doesn't make sense."
Red Bull quitting the sport would have big ramifications as the loss of both its teams - Red Bull Racing and Toro Rosso - could reduce the grid for 2016 to just nine teams. It has a contract with Formula One to remain in the sport until 2020, but Red Bull owner Dietrich Mateschitz has previously made clear that nothing will stand in his way if he decides to quit.