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Bernie Sanders got a rock star reception Wednesday when he joined some of the nearly 40,000 Verizon workers who walked off their jobs.

The Democratic presidential candidate was greeted with cheers when he showed up unexpectedly on the picket line in Brooklyn to show solidarity with striking landline and cable workers.

"Brothers and sisters, thank you for your courage in standing up for justice against corporate greed," Sanders said to loud applause.

Earlier, Sanders' rival Hillary Clinton blasted Verizon's management and sided with the strikers.

"Verizon should come back to the bargaining table with a fair offer for their workers," she said in a statement. "To preserve and grow America's middle class, we need to protect good wages and benefits, including retirement security. And we should be doing all we can to keep good-paying jobs with real job security in New York."

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Workers who belong to the Communications Workers of America (CWA), which has endorsed Sanders, and the International Brotherhood of Electrical Workers (IBEW), went on strike at 6:00 a.m., gathering in midtown Manhattan and at more than 20 other locations from Massachusetts to Virginia.

Their contract expired in August and management has yet to negotiate satisfactory terms, they say, as Verizon pushes for ways to manage pricier health care for its retired and current workers and "greater flexibility" over its employees.

"We're striking for a fair contract," David Doran, a field technician for Verizon told NBC's News Channel 4. "The company wants to outsource our work to other countries. We believe there's enough work here that can be done by the people in the union now."

"Our families and customers deserve more from Verizon," Isaac Collazo, a technician and CWA member from Brooklyn who has worked at Verizon for 19 years, said in a statement. "Through our hard work, Verizon is making record profits while our families are left with threats to our jobs and our customers aren't getting the service they need. Striking is a hardship for our families, but we need to remind Verizon executives that the people who build their profits are a critical reason for the company's success."

Bob Mudge, president of Verizon's wireline network operations, said they were expecting the strike.

"Let's make it clear, we are ready for a strike," said Mudge.

Verizon has trained thousands of non-union workers and moved staff to other locations to fill spots made vacant by picketers.

The replacement workers, Mudge said, "know our first priority is maintaining services for our customers and they have taken on this challenge with pride."

The last time Verizon workers went on strike was in August 2011 and it lasted two weeks. Neither side would estimate how long this job action would last.