Under the watch of new F1 owners Liberty Media, the schedule will increase from 20 to 21 races in 2018, amid apparent plans for up to 25 grands prix in the near future.
Spaniard Alonso has said that if that happens he will quit F1, and Montreal winner Lewis Hamilton said at the weekend: "I understand what Fernando's saying and tend to agree with him."
With a similar opinion is Lauda, an F1 legend who doubles as Mercedes' team chairman.
"21 races is the maximum," the great Austrian told Osterreich newspaper.
"More would be nonsense, as F1 would become like the Ski world cup, where people are overloaded."
Meanwhile, Lauda rubbished Eddie Jordan's recent claim that Mercedes intends to quit F1 after the 2018 season.
Asked how he responds to the former F1 team owner's comments, Lauda said: "It's best not to at all. But he doesn't know what he's saying."
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