Even General Motors' pledge to build a works Formula 1 engine by 2028 hasn't changed the top team's opposition to an eleventh team spot for Andretti.
Andretti-Cadillac has the FIA's green light, but opposition from the majority of the teams is adding fuel to Liberty Media's troubled commercial talks with the hopeful American project.
GM, however, gave the bid a major boost this week when president Mark Reuss announced that he is "thrilled that our new Andretti-Cadillac F1 entry will be powered by a GM power unit" a few years into the project in 2028.
Williams boss James Vowles, however, is unimpressed.
"I don't know what the relationship is between those two entities," he said in Las Vegas.
"GM, I think, is a good company to bring into our sport. But my view hasn't changed on the addition of an eleventh team," Vowles added, explaining that his concerns are about "the finances of Williams".
Mercedes chief and co-owner Toto Wolff is also still lukewarm about Andretti.
"You know, we need to see whether the commercial rights holder deems this to be a good entry or not," said the Austrian. "For many teams it is big dilution that can make the difference between, you know, big losses or less losses.
"I haven't changed my opinion on that. We haven't seen any data. Where's the case? What are the numbers? How much can we gain in popularity? What's the name worth? How much more can the sport be attractive? What are the facts?"
Frederic Vasseur, of Ferrari, insisted that while GM is "welcome in F1", that does not mean Michael Andretti gets the same welcome.
"It's not the same story as the eleventh team," he said. "It's two separate questions."
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