US Volkswagen head Michael Horn has said he first learned last year about problems with the automaker's diesel engines. Lawmakers in Congress will grill him over how much he knew about the rigging of emissions tests.
In a written statement to Congress, Horn said he first learned about possible "emissions non-compliance" early last year.
He is scheduled to testify before a House subcommittee on Thursday. The 51-year-old German took control of the firm's US subsidiary last year.
Millions of vehicles falling under Volkswagen's various brands have been found to have on-board software developed by the company to deceive emissions testers.
Following the publication of a study by the West Virginia University early last year, Horn said he was "told that there was a possible emissions non-compliance that could be remedied."
"I was informed that EPA regulations included various penalties for non-compliance with the emissions standards and that the agencies can conduct engineering tests which could include "defeat device" testing or analysis. I was also informed that the company engineers would work with the agencies to resolve the issue," according to the statement.
Horn goes on to say that he understood technical teams had a plan "to bring the vehicles into compliance."
"On behalf of our company, and my colleagues in Germany, I would like to offer a sincere apology for Volkswagen's use of a software programme that served to defeat the regular emissions testing regime," Horn said in his statement.
"These events are deeply troubling. I did not think that something like this was possible at the Volkswagen Group. We have broken the trust of our customers, dealerships, and employees, as well as the public and regulators."
The statement said Volkswagen plans to withdraw applications seeking US emissions certifications for its 2016 model vehicles. The withdrawal raised the possibility that software similar to earlier models is also included in its new cars.
The scandal has shocked the car industry and even raised questions about the "Made in Germany" brand as a whole.
'Execs didn't know'
Volkswagen's new chief executive, Matthias Müller, was quoted Wednesday as saying that the investigation so far had found that a few software developers had tampered with the pollution controls on some diesel engines. Top executives, he said, would not have gotten involved in the software.
Müller told the Frankfurter Allgemeine Zeitung he did not rule out the possibility that there might be a wider circle of offenders, and added that the carmaker was "now clarifying the responsibilities in detail."
Volkswagen has so far suspended four people responsible for engine development and brought in a law firm to investigate. The firm says it will need more than a year to complete a recall of affected vehicles, many of which are also believed to be in Europe.
rc/jr (AFP, AP, dpa, Reuters)