(Reuters) – Tens of thousands of Verizon Communications Inc. workers walked off the job on Wednesday in one of the largest U.S. strikes in recent years after contract talks hit an impasse.

The strike could affect service in Verizon’s Fios Internet, telephone and TV services businesses across several U.S. East Coast states, including New York, Massachusetts and Virginia.

The strike was called by the Communications Workers of America and the International Brotherhood of Electrical Workers that jointly represent nearly 40,000 employees, such as customer services representatives and network technicians in Verizon’s traditional wireline phone operations.

Workers protested at various Verizon locations along the East Coast. Verizon said it had trained thousands of non-union employees over the past year to ensure no disruption in services.

While the wireline unit represents Verizon’s legacy business, it generated about 29 percent of the company’s revenue in 2015 and less than 7 percent of operating income.

Verizon’s Fios TV and Internet service is no longer growing and the company has been scaling back its landline network as it has shifts to the bread-and-butter wireless business and new efforts in mobile video and advertising.

Verizon and the unions have been talking since last June over the company’s plans to cut healthcare and pension-related benefits over a three-year period.

The workers have been without a contract since its agreement expired in August. Issues include healthcare, offshoring call center jobs, work rules and pensions.

“It’s regrettable that union leaders have called a strike, a move that hurts all of our employees,” Marc Reed, Verizon’s chief administrative officer, said in a statement on Wednesday. “Since last June, we’ve worked diligently to try and reach agreements that would be good for our employees, good for our customers and make the wireline business more successful now and in the future.”

The last contract negotiations in 2011 also led to a strike. A new contract was reached after two weeks.

On Tuesday, Verizon said it has been approached by the Federal Mediation and Conciliation Service. In the last round, the FMCS mediated their contract dispute.

“The question of federal mediation is a distraction to the real problem: Verizon’s corporate greed,” the unions said in a statement, adding it has not yet contacted the FMCS.

Verizon’s shares dipped 0.1 percent at $51.88.

(Reporting by Malathi Nayak and Rishika Sadam; Editing by Saumyadeb Chakrabarty; and Jeffrey Benkoe)