Bernie Ecclestone says existing Formula 1 teams are "afraid" of losing money by agreeing to green-light an eleventh entry.
FIA president Mohammed ben Sulayem says it's "surprising" that, notwithstanding Cadillac and General Motors joining Andretti's F1 team bid, there are still so many "negative reactions" in the paddock.
However, one such critic - Mercedes' Toto Wolff - at least admits that Andretti is making a bold "statement" by teaming up with Cadillac in their bid.
Nonetheless, it is rumoured that some teams are now pushing for the compensatory fee payable by Andretti to swell from $200 million to as much as $700 million.
Those same teams are reportedly also demanding that Cadillac be unable to simply re-brand a Renault or Honda customer engine.
"It won't be just an engine rebrand," Forbes quotes Michael Andretti as insisting. "The intellectual property of Cadillac will be invested in the engine."
Andretti's famous father Mario added: "It's not a PR gimmick. GM has its pride.
"They don't just want to hang onto something - they want to bring in the technology themselves. That's what interests them about the project," he told Auto Motor und Sport.
Indeed, the FIA has now commenced an 'expressions of interest process' for up to two new team entrants.
"The maximum is 12 teams," president ben Sulayem insists.
He added: "We're talking here about GM, one of the top five car manufacturers in the world.
"We have to promote something like that. It would also be a team from the USA, which would be important for Formula 1."
According to former F1 supremo Bernie Ecclestone, the resistance of the teams to an Andretti-Cadillac entry is simply due to financial reasons.
"The Andretti name would be very good for the sport, which is now spreading more and more in America," he told the Swiss newspaper Blick.
"Many teams are simply afraid that they will have to share the billion dollar cake with an eleventh team," Ecclestone explained.
"But according to the rules, only the ten best teams earn so what is the problem? Up to two years after they come in, nothing would change anyway."
Michael Andretti commented: "No one would be able to understand if Formula 1 rejected a large American manufacturer.
"And if Ford were to come in too, then that would be a dream. Whatever happens next, I want to stay positive."
