Stalled contract negotiations led thousands of workers in Verizon Communication Inc.’s wireline division to go on strike Sunday, potentially affecting landline operations as well as installation of services like FiOS, its fiber-optic television and Internet lines.

The contract for the 45,000 employees from Massachusetts to Washington, D.C., expired at midnight Saturday with the company and the workers unable to come to terms on issues including health care costs and pensions.

Verizon offers landline service in Connecticut, California, Delaware, the District of Columbia, Florida, Maryland, Massachusetts, New Jersey, New York, Pennsylvania, Rhode Island, Texas and Virginia.

The dispute does not affect the company’s wireless division. Verizon is the nation’s largest wireless carrier.

Verizon employees who are members of the Communication Workers of America union picketed headquarters in New York City on Sunday morning, wearing red and holding signs with messages including “CWA on strike for middle-class jobs.”

Vinnie Galvin, 56, said he and his fellow workers are the backbone of the industry. “Everybody needs to be wired and we’re the people who do that,” said the three-decades-plus veteran of the company.

“They’re trying to bust us. … This is stuff that it took us 40, 50 years to get.”

The affected workers are responsible for maintaining and repairing traditional landlines, as well as installing FiOS, union spokesman Bob Master said.

Workers covered by the expired contract also include 10,000 represented by the International Brotherhood of Electrical Workers, who serve as telephone and repair technicians, customer service representatives, operators and more. Contract negotiations began June 22.

New York-based Verizon has 196,000 workers; 135,000 are nonunion.

The company is asking for changes in the contract because it says its wireline business has been in decline for more than a decade as more people switch to using cellphones exclusively. It had 25 million landlines at the end of the second quarter, down from 26 million at the end of 2010. It has been selling off some of its landlines to other phone companies.

“It’s not reflective of today’s marketplace,” Verizon spokesman Rich Young said of the contract. “Our union employees pay nothing toward their health care premiums. That’s virtually unheard of.”

Master said the company wanted worker concessions at a time when it was making billions in profits and top executives were making millions in salary.

“We have never seen such a sweeping attack on the quality of life of our members,” he said. “This is an unprecedented and in our opinion completely unjustified attack on middle-class jobs.”

Young refuted the union’s contentions on Verizon’s profits, saying that the wireline unit was declining overall despite the growth of products like FiOS.

Master said the strike could impact customers looking for installations or repairs to their service, but Young said Verizon had taken steps like training managers and retirees.

Young said Verizon would return to the table at any point, that it was up to the union. The union said workers would be prepared to return to work when Verizon demonstrated a willingness to bargain seriously.