Mercedes has opted to quit the series at the end of 2018 in favour of Formula E, meaning the DTM is currently facing the prospect of just Audi and BMW competing in ’19.

Motorsport.com understands a variety of options are being considered for the future, including ongoing talks of a mooted ‘Class One’ with Super GT and a “bridging year” with Audi and BMW.

Berger says he has spoken with almost all internationally recognised manufacturers and that recent intensive discussions with the Volkswagen Group failed to come to a resolution.

When Motorsport.com asked if Audi and BMW were helping the search for a Mercedes replacement, Berger said: “I don’t know.

“Until now, we didn’t go into a deeper discussion [with Audi and BMW over the future] because I do not give up and I cannot believe with this great platform it is not attracting the other manufacturers.

“It is very difficult to say [why there is no interest]. For some it is political and for some, it is too German. There are different issues, but I still believe somebody would have a great platform.”

The DTM has added a return to Britain at Brands Hatch and a night race at Misano, which Berger says is part of a deliberate push to be “more international”.

Berger hopes that strategy rewards the DTM with a European, non-German, manufacturer.

“Another big help would be to have a European manufacturer,” he said. “It would be fantastic if it was German, but it would be at least as fantastic to have a European [manufacturer] as a sign of a good direction.

The DTM has not given a deadline for a new manufacturer to make the grid for 2019, but that the next eight weeks are crucial for clarity.

“Honestly, it’s very, very difficult to say,” said Berger. “It’s the next eight weeks where things have to become a bit more clear, but again, we have a very strong TV number for the first time in a while.

“I really cannot believe, and it cannot be that the Mercedes decision that stops this platform from working.”

Ekstrom: DTM needed Mercedes

Mattias Ekstrom, who has now exited the series after 17 years with Audi, says that the series will struggle to recover because Mercedes is the cornerstone of the DTM.

Mercedes is celebrating "30 years of DTM" in 2018 having raced in the series and its predecessor between 1988-2018.

“I think it is difficult to see in my world, Mattias Ekstrom’s world, how DTM can go so far without Mercedes,” he told Motorsport.com.

“In my opinion, DTM, in the beginning, was Mercedes. I struggle to see a DTM without Mercedes getting to the same standing.”