Portland sued Uber on Monday to stop the fast-growing ride-hailing service from operating in the Oregon city until it follows local regulations.
Uber operates in areas around Portland, but only started up in the city itself on Friday, without consent from authorities or any agreement over how it should be regulated.
"The city's lawsuit is asking for a declaration by the court that Uber is subject to the city's regulations," the city said in a statement. "The lawsuit also asks the court to order Uber to stop operating in Portland until it is in compliance with the city's safety, health and consumer protection rules."
Uber did not immediately respond to a request for comment. The company's website does not currently list Portland, Oregon, as a location where it operates, but local media reported that the service has been available there for the past few days.
The online ride service was valued at $40 billion last week after its latest funding round ahead of an expected initial public offering.
However, it has been dogged by controversy surrounding its aggressive approach to local governments and traditional taxi services.
It has been banned from taking bookings in the Netherlands because authorities say it lacks a special license.
On Monday Uber was banned from operating in the Indian capital New Delhi after a female passenger accused one of its drivers of rape.
The case is City of Portland v Uber Technologies Inc, filed in the Circuit Court of the State of Oregon for the County of Multnomah.
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