A judge opened the door Wednesday to expanding the number of drivers who can join a class-action suit against Uber contending they are treated like employees but get no employee benefits.

US District Court Judge Edward Chen said that even those who accepted a contract that called for arbitration of disputes could join the lawsuit, saying the arbitration agreements are "unenforceable."

The ruling opens the door to as many as 160,000 Uber drivers in California who have worked for the ride-sharing service dating back to 2009.

The suit filed against Uber argues that drivers qualify as Uber employees as opposed to independent contractors and, as such, are deserving of benefits and protections called for by California labor law.

In particular, those behind the suit contend that Uber has failed to reimburse drivers for expenses or losses related to doing their jobs and has failed to pass on tips from riders.

The case is among several pending in US courts about workers in "on-demand" or "sharing economy" platforms who are considered independent contractors and get no social benefits, and contend they should be treated as employees.

Uber and its peers argue that the platforms offer far more flexibility that employees would get, and that in many cases the workers earn more.

A statement from Uber said it would appeal the latest ruling.

"Nearly 90 percent of drivers say the main reason they use Uber is because they love being their own boss," the statement said.

"Drivers use Uber on their own terms; they control their use of the app along with where and when they drive. As employees, drivers would lose the personal flexibility they value most."