Red Bull owner Dietrich Mateschitz has once again threatened to quit the sport, saying he'll only stick around if he has a "competitive" team.
Having won four consecutive Championship doubles from 2010 to 2013, Red Bull Racing lost out to Mercedes last season.
The first year under the 1.6-litre turbocharged V6 engines heralded a change at the top as Mercedes produced the best engine in the field while Renault, who supply Red Bull, struggled with reliability and pace.
That form has continued into this season leading to yet more threats from Red Bull to withdraw from the sport.
"We'll only stay in Formula One if we have a competitive team, and we need a competitive power unit for that," Mateschitz told the Austrian Press Agency.
"If we don't have one, we can race with the best car and the best drivers and still have no chance of competing for victory."
Mateschitz also ruled out Red Bull producing their own engines.
He said: "The problem is, we can't control it.
"We are not a car manufacturer who could justify the investment. So we rely on Renault to close the gap to Ferrari and, above all, Mercedes."
The Austrian businessman also didn't rule out their current lack of form resulting in Renault pulling out of F1.
"Of course Renault can also weigh its options, including a pullout," he said.
"As a manufacturer, it's your task to deliver a competitive power unit. If you can do that, it's great. If, for whatever reason, you can't do that, you should pull out.
"Then the consequences for us would be clear, too."