Volkswagen shares rose ahead of a crucial meeting later today at which its chief executive will try to persuade US authorities to accept a fix for thousands of cars rigged to cheat diesel emissions tests.
The meeting with the Environmental Protection Agency is Volkswagen's best chance for some time to draw a line under a crisis that erupted four months ago when it admitted to cheating the US tests.
CEO Matthias Mueller is on his first visit to the US since the scandal broke.
He said over the weekend he believed a new catalytic converter system could be fitted to most affected US vehicles that would satisfy regulators.
However, the meeting with the EPA risks being overshadowed by an interview in which Mueller appeared to play down the seriousness of the cheating by Europe's biggest carmaker.
In comments aired by National Public Radio (NPR), Mueller blamed the scandal on a misunderstanding and called it a technical, not an ethnical, problem.
The remarks, coupled with the time it has taken Mueller to visit the US since being made CEO in September, have raised fresh questions over VW's handling of the crisis.
A union source close to VW's supervisory board said he was "astonished" by Mueller's remarks.
"This is a key week for Volkswagen as it struggles to regain ground in the US. Those comments are anything but helpful and should have never been made," he said, speaking on condition of anonymity.
Analysts said that obtaining the goodwill of US authorities could be crucial in reducing civil or criminal penalties the German carmaker is likely to face.
After VW asked to redo the interview, Mueller - who is not confident in English - told NPR he had found the situation hard to handle as he was in a loud environment hemmed in by reporters when he made his comments at the Detroit auto show, and apologised to customers, dealers and authorities.
US environmental regulators are unimpressed with VW's efforts so far to redeem the damage done through the emission of 40 times the legal limit of nitrogen oxide by its 2.0 litre diesel cars over seven years.
"VW's submissions are incomplete, substantially deficient, and fall far short of meeting the legal requirements to return these vehicles to the claimed certified configuration," the California Air Resources Board wrote in a letter to VW earlier this week.
VW said the letter referred to its initial recall plans submitted to California in December.
CARB said it would continue to work with the carmaker and the EPA to find a solution, but emphasised the danger to public health that VW continued to pose.