Andretti announced on Thursday that it had reached a deal with GM to lodge an expression of interest with the FIA to enter F1 as soon as it could. If successful, the team will run under the Cadillac banner.
The involvement of GM in the project has caused a surprise because it is not thought the American manufacturer had any intention of building its own F1 power unit from 2026, with the registration deadline having now passed.
However, GM president Mark Reuss has clarified that an agreement has already been reached with a current F1 engine manufacturer to use its power unit initially.
"We have a signed agreement with a power unit supplier to begin with," he said. "And then, as we move forward, we bring a lot of our expertise to create things for the future as well."
Michael Andretti added: "It'll be more of a collaboration, I think, with another manufacturer."
While neither Reuss nor Andretti offered any details of which manufacturer it was planning to work with, the most logical one would be Honda.
The Japanese manufacturer officially withdrew from F1 at the end of 2021, but recently revealed that it had registered with the FIA to be able to produce a power unit for the 2026 regulations. It has also shown itself willing to let other companies re-badge its products, having leased out its IP to Red Bull for the next few years.
Furthermore, Cadillac and Honda have a long-standing automotive business collaboration regarding electric vehicles so the two companies already have good ties.
Asked specifically about Honda being its planned partner, Reuss said: "On the EV part of it, obviously we do have a large partnership with Honda. We also compete against Honda in series like IndyCar as well.
"So we have that natural respect and relationship, which is not problematic at all. We'll talk about the engine piece of this at a later date."
The other option Andretti had been looking at was Renault, with the French car manufacturer eager to add customers to its roster in the future.
Red Bull has also been looking at finding a manufacturer partner to badge its own power units from 2026 and has most recently been linked with Ford.
For GM, the chance of a partnership with an entry of the calibre of Andretti, allied to the ability of it having ready access to F1-spec engine technology from the off, meant that a move into grand prix racing made sense.
Speaking about why GM was looking at F1 now, Reuss said: "Along the history of at least my career, we would have loved to have gotten into Formula 1, but for various reasons it was pretty tough to do that.
"Whether it was the leadership, or the amount of money at that time, or where the company was, where the economy was, whatever those reasons were, over a long period of time, they were different."
Andretti says it has already started recruiting engineers for its F1 project, and has lined up a technical director.
"We've done a lot of hiring," said Andretti. "We have quite a few people already working for us. We have hired the main engineers. So yes, we're very much down the road and all that. We have our technical director already hired, and we will announce that down the road as well."
