There's a warning this weekend for Uber users. It may be difficult to schedule a ride in the company's biggest cities.

A group calling itself UBER Freedom has organized a strike in cities like Chicago, Los Angeles and Houston demanding higher fares, Mashable reported.

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The strike was scheduled to start Friday and continue through the weekend, according to the event's Facebook page.

The self-proclaimed ride-sharing service allows drivers to register with the company and pay the company a portion of the fares when app users book rides, WRC reported.

Drivers say they are not being paid enough and are demanding a 60-percent rate increase for Uber X rides, a $7 minimum fare, a $7 cancellation fee and an option for users to leave tips on the app.

Uber started in 2009 and boasts about 162,000 drivers in the U.S.

The service allows drivers to work when they want by starting the app when they're able to take fares. Drivers are treated like independent contractors, Mashable reported.