US prosecutors have sued Uber over allegations it violated disabled passengers' civil rights.

US authorities argued in a lawsuit Wednesday that ride-share firm Uber violated civil rights protections by imposing "wait" fees on disabled passengers who needed extra time to board a vehicle.

Uber charges a fee if a driver has wait more than two minutes to pick up any , but the Department of Justice said applying those costs to handicapped riders amounts to unlawful discrimination.

"This lawsuit seeks to bring Uber into compliance... while sending a powerful message that Uber cannot penalize passengers with disabilities simply because they need more time to get into a car," said Assistant Attorney General Kristen Clarke in a statement.

Uber called the suit "surprising and disappointing," saying it had been in discussion with authorities on the matter.

The firm added it had refunded wait fees to handicapped passengers, and since last week any rider who certified they are disabled will have the charges automatically waived.

US prosecutors said the company has failed to "reasonably" modify its policy, noting that a passenger may use a wheelchair that needs to be folded and stored in the car or a blind rider may require additional time to safely walk to the vehicle.

The suit asked a in northern California to order Uber to change its wait time fee policy to comply with the Americans with Disabilities Act (ADA).

It also wants the court to order Uber to "train its staff and drivers on the ADA, pay money damages to people subjected to the illegal wait fees and pay a civil penalty."

The company already faces lawsuits from a series of passengers in the United States alleging they were victims of assault during Uber rides.

It has also fought court and ballot box battles in California, along with ride-share company Lyft, over whether drivers should be considered employees and thus entitled to certain benefits.