Red Bull motorsport consultant Helmut Marko says Formula 1 chiefs must come up with an independent engine solution for 2021 during this year or risk losing his team.
In a meeting between the FIA and manufacturers both in F1 and not currently involved last month, it was agreed that the current turbocharged V6 hybrid power unit format should be replaced by cheaper, simpler and noisier engines from 2021.
But speaking in an interview with the official F1 website, Marko warned that the championship's new owner Liberty Media must ensure there is a non-manufacturer engine option within that rules package to keep Red Bull in the championship - and that F1 has to get that plan in place this year.
The drinks firm's two F1 teams, Red Bull Racing and Toro Rosso, are both currently customers of Renault.
"The latest must be 2021 that an independent engine supplier comes into F1," Marko said. "This is more than necessary, and the engine has to be simple, noisy and on the cost side below 10 million.
"We are talking about a much less sophisticated engine than what we have now, a simple racing engine. There are enough companies around that could supply.
"So we expect from the new owners together with the FIA to find a solution at the latest by the end of this season.
"If that doesn't happen our stay in F1 is not secured."
Red Bull, which like the other nine current F1 teams has signed up to the championship to 2020 at present, was a factory partner of Renault during its dominant seasons at the start of the decade.
But discord over Renault's poor performance and reliability in the early years of the hybrid formula took the relationship to breaking point.
While Renault bought Lotus to revive its works team programme, Red Bull held abortive talks with Mercedes, Ferrari and Honda during 2015 before returning to Renault and agreeing a customer deal under which the engines would be badged TAG Heuers.
F1 engine supplies have been exclusively provided by major car manufacturers since Marussia dropped Cosworth in favour of Ferrari at the end of 2013 ahead of the following season's rule changes.