Red Bull have until the end of May to decide whether they want to continue with Renault engines in 2019, or switch to Honda power.
With Toro Rosso swapping to Honda for 2018, Red Bull have opened up options for the future as Christian Horner recently acknowledged.
“All things are open for 2019 onwards,” said the Red Bull team boss.
“We will play close attention to how things develop at Toro Rosso, but there are no preconceptions as we head into the season.”
Renault, though, have made it clear that they expect a decision by the “end of May” as they look to confirm their plans for next season.
“We are not going to hang around forever,” Renault boss Cyril Abiteboul said when asked by Motorsport.com. “I know what Christian is referring to when he says that he has options.
“He’s absolutely right. Like him I read contracts, and I know the obligation that we have towards the sport.
“There is one thing that is clear, and that is planning. And there will be a deadline for Red Bull Racing to define what they want for the future. It’s available, it’s in the Sporting Regulations.
“I believe that by the end of May there needs to be some clarity as to who is supplying which team – which supplier is supplying which customer team. As far as we are concerned, that will be the deadline.”