Audi has revealed it will remain in the DTM in 2019 but says a third manufacturer must be found by 2020 for a "continuing" commitment.
Head of Audi Motorsport Dieter Gass all but confirmed the manufacturer would remain in the series in 2019 at Brands Hatch earlier this month, despite the impending withdrawal of Mercedes at the end of 2018.
He laid out plans for Audi to expand to at least eight cars for a "minimum" 16-car grid next year, as the championship transitions into its new 'Class One' era with turbocharged engines.
Audi has now officially communicated it will remain in the DTM, alongside its Formula E project that yielded the season four manufacturers' title, but in a statement said "a minimum of three brands being represented from 2020 on at the latest will be the prerequisite for Audi's continuing DTM commitment."
Aston Martin has been tipped to join the DTM field in 2020 in a possible partnership with AF Racing - the company behind the R-Motorsport GT team - HWA and Red Bull.
"Thanks to forward-thinking technologies like the new turbo engines, we continue to see major potential [in the DTM]," said Gass.
"Concerning the third manufacturer this will require, I have great confidence in DTM boss Gerhard Berger bringing this competitor to the grid for 2020 at the latest."
BMW motorsport boss Jens Marquardt also reemphasised his brand's DTM commitment at last weekend's Misano round.
"We fully support the DTM and we are committed," he said. "We need to have the commitment of a third manufacturer in 2020, but this is the ITR's job."