US prosecutors confirmed Friday that charges against Volkswagen executive Oliver Schmidt would be reduced after he pleaded guilty to his part in covering up the German carmaker's "dieselgate" emissions-cheating scandal in the US.

Schmidt, who led the German automaker's US regulatory compliance office until 2015, appeared in a Detroit court to enter his plea. He had pleaded not guilty before his change of mind.

US prosecutors said they would drop a wire fraud charge, which carried a maximum penalty of 20 years in prison. But they retained a fraud conspiracy charge and a charge of violating the US Clean Air Act, which together carry a maximum sentence of seven years.

Also under the plea agreement, Schmidt may have to pay a fine of between $40,000 (34,000 euros) and $500,000. The final verdict is due December 6, 2017.

In 2015, VW admitted it had equipped about 11 million cars worldwide with defeat devices to evade emissions tests, including about 600,000 vehicles in the United States. Diesel cars marketed as clean were in fact emitting 40 times the permissible limits of nitrogen oxide during normal driving.

Altogether eight managers from the German car group are facing charges by US authorities for the company's breach of emissions regulations. Many of the other managers charged are believed to be in Germany, making extradition to the US unlikely.

Schmidt was the second VW employee to plead guilty, after former company engineer James Liang admitted last year to helping devise the defeat devices. An FBI affidavit cited him as a cooperating witness.

In March, VW agreed to pay $4.3 billion in penalties after pleading guilty to conspiring to violate the US Clean Air Act. That was on top of $17.5 billion in civil settlements. The carmaker still faces an array of legal challenges in Germany and worldwide, and has so far set aside more than 22 billion euros to cover dieselgate costs.

Audi chief under increasing pressure

Media reports by German public broadcasters NDR and WDR and by the Süddeutsche Zeitung daily said Friday that Audi CEO Rupert Stadler was in the firing line after incriminating evidence allegedly given by witnesses.

The reports suggested the Audi boss had hindered investigations by US environmental authorities into Volkswagen's emissions-cheating practices. It appeared that after the VW scandal broke in late 2015, Stadler had told other managers to remove vital information from prepared presentations on how Audi diesel engines and their emissions control technology worked.

The presentations, meant to be shown to US investigators and compiled with a view to answering questions about Audi's 3.0-liter diesel engines, were said to have been shortened in such a way that would have made it impossible to discover any form of emissions data manipulation.

So far, Stadler has always insisted he'd only learned about VW's emissions-cheating practices when US agencies made them public.

uhe/rd (AFP, dpa, Reuters)