Mercedes have come out in opposition to Liberty Media's proposed new engine formula for 2021.
On Tuesday, the German marque as well as Ferrari, Renault, Honda and other manufacturers including Porsche got together to hear the new F1 owner's plans for the next-generation engine.
Liberty wants the 2021 engine to be louder, cheaper, simpler and provide a more level playing field.
It will be based on the same 1.6 litre V6 base, but without the controversial MGU-H, with higher revs, and with standard batteries and a more "prescriptive design".
However, Germany's Auto Bild claims that Ferrari, Mercedes and Renault are already opposed to the Liberty vision, which will now be discussed at a series of follow-up meetings.
Mercedes's Toto Wolff told Auto Motor und Sport: "The concept sounds similar to what we have now.
"But it means a completely new development that will mean we are working on two engines at the same time between 2018 and 2020."
However, Red Bull are happy.
"An engine like that is good for us," said Dr Helmut Marko.
Yet it appears that existing manufacturers like Mercedes are not ready to give up the argument for engines that are more like the current 'power units'.
"It's a vision rather than a regulation," Wolff said of Tuesday's Liberty presentation. "And it's their vision rather than the manufacturers'.
"It is important to define all together what Formula 1 should be in 2021, not just from the point of view of the engine. What we have is the starting point of a dialogue rather than something we have agreed to.
"Certain things are right, but it's not quite there."
However, he insisted that Mercedes are not necessarily shaping up for war with Liberty.
"I just want to make it clear that there are different opinions," said the Austrian. "It was a presentation by F1's management, we will now wait and see what is put on the table next week and start a dialogue from there."
The 2017 calendar continues with the Brazilian Grand Prix next Sunday.
