The R-Motorsport Aston Martin squad has decided against competing in the DTM's joint-race with SUPER GT at Fuji in November, leaving only BMW and Audi to represent the German series.
While DTM boss Gerhard Berger told select media that the decision was "not confirmed yet", Autosport has been told that R-Motorsport and Aston's decision is final.
Autosport had previously been told that R-Motorsport was mulling over its driver line-up decision for Fuji but, following talks between R-Motorsport and Aston, the decision has now been made to withdraw from the Fuji event.
Instead, R-Motorsport and Aston will prioritise the 2020 development of its Vantage DTMs as it continues to make up for its late commitment to the series in '19 and improve its HWA-built, Aston-branded engine's weakness.
When Autosport asked R-Motorsport team principal Florian Kamelger whether Aston had decided on its Fuji plans, he said: "Yes, I have.
"I'm regrettably having to say we won't be in Fuji because we [want to] focus 100% on 2020 season.
"We took that decision together with Andy [Palmer, Aston Martin CEO] and with Aston.
"I know it is a frustrating message to the outside world.
"Nevertheless, I know that this is the first one of many and we more than ever 100% committed to do the world series between the DTM and Super GT and go into Super GT [in the future] too."
While the DTM will only send "between six and 10 cars" to Fuji, R-Motorsport's cars would have been away from its base for a month and the team believes it would have impacted its development plans.
The squad also has the smallest budget in the series - believed to be €20million - and Kamelger said costs of the Fuji race and logistics played a part in its decision.
Kamelger had previously raised concerns over the DTM's SUPER GT future at the Lausitzring round.
When Autosport asked if Berger could understand R-Motorsport and Aston's reasoning, he said: "Yeah because they are really fighting [with] a limited number of people.
"I'm on one side [disappointed] if they don't come to Japan, but on the other side the most important thing is next year to have three manufacturers from the beginning fighting for the win [in DTM]."
During Berger's press conference, other details about both SUPER GT's Hockenheim presence and the Fuji joint-event were confirmed by the DTM.
Of the SUPER GT line-up at Hockenheim, only 2009 Formula 1 world champion Jenson Button will compete in both races, with Lexus and Nissan sharing their driving duties out.
The SUPER GT field will also have two one-hour practice sessions ahead of the Hockenheim round to help with the equalisation process.
For Fuji, both BMW and Audi are set to confirm driver line-ups at Hockenheim - with Audi keen to involve customer squad WRT too - and Berger told Autosport that the DTM will not influence the manufacturer choices.
TV details are still being negotiated for the Fuji joint-event but, in regions where a TV broadcaster does not pick up the rights, the DTM will offer a live stream.