Toto Wolff has warned of the possibility Mercedes could downsize its customer power unit supply as the current arrangement is no longer financially "compelling".
Since the introduction of the current 1.6-litre turbo-hybrid systems in 2014, Mercedes has dominated the sport, guaranteeing it a healthy customer supply.
At present, McLaren, Aston Martin and Williams all use Mercedes power units but it now appears one is in danger of being dropped as the supplier is no longer earning "substantial amounts", according to Wolff.
“Unfortunately, the business of leasing engines is not compelling and interesting because the FIA has put in a certain limit that you can charge to your customers, in order to protect the smaller teams,” said Wolff, speaking to the Financial Times.
“I’d rather have six [client cars], push the development further down the line and then make two engines less, because you need to produce two less plus two spares for every team.
“In an ideal world, I would maybe see us plus two [customers], so actually downsize a bit."
Wolff declined to elaborate on which of the three customers would likely make way if a firm decision was taken to "downsize".
New power unit regulations are due to come into force in 2026, with the likelihood Audi and Porsche will enter at that stage.