Volkswagen could reach a "final" settlement with US regulators as early as October over its large engine diesel cars that cheated emissions tests, Audi's sales chief has said.

Dietmar Voggenreiter, Audi's head of sales and marketing worldwide, told Reuters in Hong Kong negotiations related to three-litre diesel VW and Audi cars were progressing well.

"(We're) in really good discussions with US authorities," said Voggenreiter. "Hopefully in October, latest the beginning of November, we will have the final agreement with the US."

The diesel emissions scandal, affecting roughly 11m vehicles worldwide has resulted in Audi set to miss profitability targets this year and the core VW brand recording a 12% year-on-year drop in profit in the second quarter, the news agency noted.

After admitting using sophisticated secret software in cars to cheat on exhaust emissions tests, VW agreed with USauthorities in June to pay up to US$15.3b for car buy-backs and repairs to 475,000 two-litre VW and Audi diesel vehicles.

But that agreement did not include repairs for around 80,000 VW, Audi and Porsche three-litre (V6) engine cars that could potentially cost billions more if the automaker needs to buy them back.

Voggenreiter also told Reuters the US negotiations, which related to four-cylinder VW diesel cars and the V6 engine Audi vehicles, were still ongoing and unresolved.

"We are just in discussions so I cannot judge how the authorities will judge our technical solutions; but I feel we have good technical solutions," he said.