The United States federal government has moved to sue Uber citing claims of discrimination against disabled people by charging an additional amount when drivers have to wait for customers to board the vehicle, according to US media reports.

The “wait time” charge was first added to the service partially in April 2016 and eventually was taken up across the United States, according to the Department of Justice. The amount is added to the base price two minutes after the vehicle arrives at the desired location.

The lawsuit was filed in the United States District Court in Northern California, according to reports from Associated Press.

The Department of Justice said that the company stands in violation of the Americans with Disabilities Act for failing to modify its fees for those who may need extra time to get into an Uber car.

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The lawsuit alleges that Uber charged the fees even when it was aware that a delay was disability-based.

Uber said Wednesday it has been in active discussions with the Justice Department and was surprised and disappointed by the lawsuit.

“Wait time fees are charged to all riders to compensate drivers after two minutes of waiting, but were never intended for riders who are ready at their designated pickup location but need more time to get into the car,” Uber said in a statement.

Uber said its policy is to refund wait time fees for disabled riders whenever they alerted the company they were changed. As of last week, any rider who certifies they are disabled will have the fees automatically waived, the company said.

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The San Francisco-based company says the average wait time fee charged to riders is less than 60 cents.

“We fundamentally disagree that our policies violate the ADA and will keep improving our products to support everyone’s ability to easily move around their communities,” Uber said.

The lawsuit asks the court to order Uber to change its policy, train its staff and drivers and pay monetary damages to people who were subject to wait time fees that violated the ADA. It also wants Uber to pay civil penalties.