Mercedes Formula One boss Toto Wolff said he wants to cut from three to two the number of non-factory teams that race with its engines.
Wolff told the Financial Times in an interview published at the weekend that new spending rules meant Mercedes was no longer making "substantial amounts" from providing engines to others.
The Austrian said the business of leasing engines was not "compelling and interesting" because the governing FIA had limited how much customers could be charged in order to help smaller teams.
The German manufacturer supplies McLaren, Aston Martin and Williams as well as the title-winning works outfit of seven-time world champion Lewis Hamilton and George Russell.
The engines are designed and made in Brixworth, central England.
Formula One teams are subject to a $140 million cost cap this season, which the bigger ones want expanded because of rising freight costs and inflation.
"In an ideal world, I would maybe see us [Mercedes] plus two [customer teams], so actually downsize a bit," Wolff said.
Mercedes provide engines to more teams than any other manufacturer, with Ferrari supplying Alfa Romeo and Haas as well as their own factory outfit.
Red Bull use Honda technology to power their cars, as do sister team AlphaTauri, while Renault supply only their Alpine team.
Red Bull is expected to join forces with Volkswagen-owned Porsche from 2026, when new engine rules come into force, while sister brand Audi is looking for a partner and have been linked to all three Mercedes customer teams.
Williams have Red Bull-backed driver Alex Albon in their car, and team principal Jost Capito was previously Volkswagen's director of motorsport.