Helmut Marko, motorsport consultant for Red Bull's Austrian owner Dietrich Mateschitz, also told the official formula1.com website on Friday that former champions Red Bull Racing needed a competitive engine if they were to stay in the sport.
"We basically have long-term contracts at the Red Bull junior program and the whole program is based on performance. So no shoot-out, but be very clear: the one who is not delivering goes," Marko said.
Red Bull Racing have Australian Daniel Ricciardo and Russian Daniil Kvyat in an unchanged 2016 lineup while sister team Toro Rosso have 18-year-old Dutch driver Max Verstappen and 21-year-old Spaniard Carlos Sainz.
Both youngsters made a big impression in their 2015 rookie season, with Verstappen the sport's youngest ever driver and points scorer. The new season starts in Melbourne next week.
From Toro Rosso to Red Bull
Toro Rosso serves as a feeder team for Red Bull, with both Ricciardo and Kvyat graduating from there as did four times world champion Sebastian Vettel who is now at Ferrari.
But for every success story, there have been plenty of others whose Formula One careers have ended prematurely after Toro Rosso tossed them aside.
Verstappen is seen as a champion of the future while Ricciardo is a race-winner who has become one of the sport's most popular drivers.
"Let’s see what he delivers. The second season is sometimes trickier than the first," Marko said of Verstappen.
The Austrian, a former racer himself, issued repeated warnings last year about Red Bull's commitment to the sport after they fell out with Renault and searched in vain for a competitive alternative.
They ended up with a Renault engine branded as Tag Heuer, with the luxury watchmaker joining as a partner, but Marko suggested that might be a stopgap. Toro Rosso have 2015-specification Ferrari power units.
"Mr Mateschitz has said many times that we are not in Formula One just to participate, we are here to win. The Olympic principle of just being there is not in Red Bull’s DNA," said Marko.
"The Concorde Agreement goes until 2020. But to stay that long we must have a competitive engine in the very near future," he added referring to the confidential commercial agreement between teams and rights holder.