FIA president Mohammed Ben Sulayem has insisted that Andretti's Formula 1 bid is "good for the sport" after Cadillac committed to building their own power unit.
Their push has been given significant backing with Cadillac formally registering with the FIA as an F1 power unit manufacturer, starting from the 2028 season.
The two brands are now awaiting the green light from F1 following approval from the FIA, though it is not known when a definitive decision is expected.
Ben Sulayem has been a vocal supporter of Andretti and Cadillac's campaign and after the latter confirmed work was underway on a power unit, he welcomed the news.
"Delighted with the news that GM have registered as a PU supplier for FIA F1," Ben Sulayem posted on X, formerly Twitter.
"This is a further endorsement of the FIA's PU regulations. The presence of iconic American brands Andretti and GM is good for the sport."
General Motors, under which the Cadillac name falls, said in a statement that they have begun preparing their engine for the sport's looming new regulations.
Delighted with the news that GM have registered as a PU supplier for FIA F1. This is a further endorsement of the @FIA's PU regulations. The presence of iconic American brands Andretti and GM is good for the sport.https://t.co/02TLDV2g5c
"We are thrilled that our new Andretti Cadillac F1 entry will be powered by a GM power unit," General Motors president Mark Reuss said.
"With our deep engineering and racing expertise, we're confident we’ll develop a successful power unit and position Andretti Cadillac as a true works team.
"We will run with the very best, at the highest levels, with passion and integrity that will help elevate the sport for race fans around the world."