Mercedes team principal Toto Wolff has insisted the "picture is still very unclear" around allowances for the VW Group's entry into F1.
Audi and Porsche have had plans confirmed for a "possible entry" with the former linked to McLaren and Sauber and the latter to Red Bull.
The Milton Keynes-based team will enter F1's new power unit era from 2026 as a standalone manufacturer, with the expertise from Porsche giving a vital boost to Red Bull Powertrains' operation.
Team principal Christian Horner has suggested that talks need to be had over increasing CapEx [capital expenditures] from the current $15 million value in order for a level playing field in comparison to its competitors.
CapEx are funds used by companies to acquire or upgrade equipment and buildings, which in this case would allow Red Bull's operation to quickly catch up infrastructure-wise to its rivals.
Asked for his thoughts given that Red Bull would technically qualify for the CapEx allowance as a newcomer, Wolff warned: "Well I think it is not clear yet who actually enters as a power unit supplier and who declares themselves as newcomers.
"It could well be that there is three companies from the same group that are entering as newcomers so the picture is still very unclear.
"Whether $15 million in CapEx is enough or not enough, there are much bigger topics we need to agree on which we haven't."