The DTM is in "final discussions" with Japan's Super GT series and is "very close" to a tie-up through 'Class One' rules, according to ITR boss Gerhard Berger.
The German tin-top series has remained in constant communication with Super GT over a planned transition to the 'Class One technical regulations over recent years, but those talks stalled when Mercedes announced its intention to quit the DTM in favour of Formula E at the end of 2018.
Former Audi motorsport chief Dr Wolfgang Ullrich said Mercedes' departure would help the merge as it had previously voted against new engine designs as the first step towards Class One back in 2017.
Autosport reviews the DTM season opener
More recently, the DTM and Super GT conducted demo runs at Motegi and Hockenheim as the two series strengthened their ties.
BMW and Audi both told Autosport that an ongoing lack of clarity regarding regulations meant that manufacturers were currently reluctant to replace Mercedes in the DTM, but Berger said that Class One adoption was now close to fruition.
"We are in the final discussions about the regulations but I am very confident that we can find the solution," he told Autosport.
"We also need international regulations, that means Japanese Super GT as an example, with us on the same regulations with the development costs for manufacturers as we want.
"We are very close to this."
When Autosport asked BMW about a timeline for it to review its DTM participation, its director of motorsport Jens Marquardt hinted at a Super GT tie-up.
"Number one in that direction [of establishing a platform for newcomers] is the regulations, and to communicate them with Super GT," he said.
"I think we are close towards that. That's the next step and then push on together to get a set-up for next year on the road."
Super GT was approached for comment on the possible tie-up with the DTM, and it provided a short statement.
"For the moment there is no decision. Regarding Class One, we, GTA [GT Association] and ITR are closely in discussions."
Autosport understands that Audi and BMW would consider a bridging year with only two manufacturers competing in DTM for 2019 if the Class One changes were not finalised, while speculation of a GTE backup plan was shot down by Berger.
The DTM has continued discussions to replace Mercedes regardless of developments elsewhere, with Berger admitting to Autosport he has spoken to every "premium" manufacturer in the pursuit of a third brand to join for 2019.