The FIA has confirmed six power unit suppliers have registered for the new engine regulation cycle beginning in 2026.
F1's governing body confirmed the news after Red Bull announced its partnership with Ford to help its powertrains division ahead of the implementation of the new regulations.
RBPT-Ford is included on the list, along with existing OEMs Ferrari, Mercedes and Alpine [Renault].
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Audi is also named having announced its entry with Sauber last year, but the intriguing sixth party named is Honda.
The Japanese manufacturer is Red Bull's current technical partner, having officially left the sport as a power unit supplier at the end of the 2021 season.
It had been suggested that Honda could partner back up with Red Bull for 2026, but the decision to team up with Ford has left the Sakura-based brand's plans rather unknown.
The glaring omission from the registration list is Porsche, which was understood to be nearing a deal with Red Bull before the bid collapsed over the finer details.
Audi's sister brand was supposedly the more committed to an F1 programme when Volkswagen announced plans to enter the sport, but as it stands, Porsche will not take to the grid as an OEM.
It could still enter in a branding capacity, as Alfa Romeo has done with Sauber since 2019.
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