FRANKFURT—Volkswagen AG's premium brand Audi expects to pay a mid-double-digit million euro amount for updating software installed in 3.0-liter diesel engines in Audi V6 TDI U.S. models and is seeking approval from U.S. authorities for the renewed software.

Audi AG also acknowledged that three auxiliary emission control devices in the engines weren't declared when it previously sought U.S. approval. One of these devices—the software for controlling the temperature in the exhaust-gas cleaning system—could be considered a defeat device under U.S. law, according to a company statement released late Monday.

In discussions with the U.S. Environmental Protection Agency and the California Air Resources Board late last week, Audi agreed to revise the software and resubmit it for approval, it said. It also agreed to extend the sales ban on the models in the U.S. until further notice. All three brands—Audi, Porsche and Volkswagen—are affected. The updated software will be installed once approval has been received, the car maker said.

EPA and California regulators said Friday that all 2009-2016 Volkswagen, Audi and Porsche diesel models with three-liter engines contain software regulators previously alleged could dupe emissions tests, a violation of U.S. and state clean-air laws. Some 85,000 models could be affected.

Volkswagen previously disputed that its three-liter diesel-engine models contained illegal software. U.S. and California regulators on Friday declined to say whether the auto maker continues to maintain that position. A Volkswagen spokeswoman on Friday declined to comment beyond confirming that the disputed software exists on all three-liter diesel models.

The engine was developed by Audi and is used in the Audi U.S. models A6, A7, A8, Q5 and Q7 from model year 2009 onward. Volkswagen uses the engine in the Touareg, while Porsche has used it in the Cayenne since model year 2013. All affected models continue to be safe and roadworthy, Audi said.

Audi parent Volkswagen is embroiled in a global emissions scandal that involves diesel and gasoline engines and could potentially cost tens of billions of euros in fines and litigation, in addition to installing new software and hardware. It has conceded it evaded nitrogen oxide emissions standards on up to 11 million diesel-powered cars. Also, it has said about 800,000 vehicles understate fuel consumption and emissions of carbon dioxide, a greenhouse gas.

The emissions scandal cost Volkswagen's former chief executive Martin Winterkorn his job and prompted the auto maker to set aside $7.3 billion to finance the cost of fixing the tainted engines.

William Boston contributed to this article.

Write to Ulrike Dauer at ulrike.dauer@wsj.com

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November 24, 2015 04:45 ET (09:45 GMT)