Mercedes motorsport boss Toto Wolff has confirmed there is no chance of a power unit partnership with Red Bull as his organisation has "no capacity".
At the start of next year, Mercedes will supply power units to four teams as McLaren joins Aston Martin, Williams and the factory Mercedes outfit.
The fact Red Bull is Mercedes' chief rival in the championship battle may also have affected Wolff's thinking, but he is confident team advisor Dr Helmut Marko already has a "plan B".
Asked if Mercedes would be willing to supply PUs to Red Bull, Wolff replied: “No, for various reasons, but the main [one] being that we are supplying four teams including us.
“We are almost in a state that we can’t make power units for all of us so there is no capacity but I have no doubt that Helmut will have a plan B and probably doesn’t need to rely on any of the current power unit suppliers.”
Honda's withdrawal from the sport leaves just three manufacturers supplying power units in Mercedes, Renault and Ferrari.
“It’s a shame Honda has decided against Formula 1," added Wolff.
“At the end of the day, each of us needs to provide a return on investment that makes sense so whatever capital you deploy for the investment in Formula 1 needs to guarantee, or needs to return, a sensible marketing value.
"If that is not the case, I can understand if somebody says ‘We’ve tried it and it didn’t function’.”
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