Volkswagen's U.S. chief apologized to lawmakers for the automaker's diesel emissions scandal, saying the the company was "determined to make things right" and prepared to accept "the consequences of our acts."
"These events are deeply troubling," Michael Horn, chief executive of Volkswagen Group of America Inc., said in three pages of written remarks ahead of a Thursday congressional hearing.
"I did not think that something like this was possible at the Volkswagen Group," he said. "We have broken the trust of our customers, dealerships and employees, as well as the public and regulators."
The German automaker has admitted installing so-called defeat devices in about 482,000 U.S. diesel vehicles and 11 million worldwide that tricked emissions tests.
The 2009-15 model year vehicles used software that lowered emissions during testing. On the road, the cars spewed up to 40 times the legally allowed amount of nitrogen oxide.
The world's largest automaker, VW faces $18 million in fines in the U.S. and possible criminal charges.
German authorities also are investigating. VW Chief Executive Martin Winterkorn resigned last month in the wake of the scandal, which has caused the company's stock price to plummet.
In addition, more than 230 class-action lawsuits have been filed against the company.
Because of the scandal, Horn said, VW was withdrawing is application for regulators to certify the emissions control devices on its 2016 model year vehicles.
Horn offered "a sincere apology for Volkswagen's use of a software program that served to defeat the regular emissions testing regime."
"Let me be clear, we at Volkswagen take full responsibility for our actions and we are working with all relevant authorities in a cooperative way," Horn said.
He said the vehicles "remain safe and legal to drive."
Two top Environmental Protection Agency official also are scheduled to testify at the hearing by the House Energy and Commerce Committee's oversight and investigations panel.
After California and federal officials discovered that Volkswagen diesel vehicles were spewing excess amounts of pollution, the company revealed that it had installed devices to trick emissions tests, one of the officials said in his prepared remarks.
"These violations are very serious," said Christopher Grundler, director of the EPA's Office of Transportation and Air Quality.
"Not only because the illegal defeat device results in excess emissions many times the allowable standard, but also because after the high emissions were discovered, VW concealed the facts from the EPA, the State of California, and from consumers," he said.
A May 2014 study by researchers at West Virginia University found that two VW diesel vehicles emitted "significantly higher" levels of the pollutant nitrogen oxide in on-road tests than in standard emissions tests, according to a memo summarizing the subcommittee's investigation.
The emissions results were shown to the EPA, the California Air Resources Board and VW, which all began investigating.
VW at first told regulators that the higher emissions "could be attributed to various technical issues and unexpected in-use conditions," said the memo, which is based on regulators' letters.
VW proposed recalibrating the emissions system of its vehicles. In December 2014, the company started a voluntary recall of about 500,000 diesel vehicles from model years 2009 to 2014.
But testing by California regulators of VW's proposed changes "showed limited improvement," prompting an expanded investigation, the memo said.
It wasn't until a series of meetings beginning in July that VW disclosed to regulators that the emissions systems in the vehicles "had a second calibration intended to run only during ... testing," the memo said.
On Sept. 3, VW admitted to the EPA and California regulators that it had designed and installed the defeat devices.
Grundler said the EPA continues to investigate and is working closely with the Justice Department, which has opened its own probe.
The EPA investigation is trying to determine "whether there are additional vehicles with defeat devices" beyond those already identified, he said.
Follow @JimPuzzanghera on Twitter.
MORE ON VW'S EMISSIONS CHEATING SCANDAL