NEW YORK — Striking Verizon employees may be back to work next week after the company and its unions reached an agreement in principle for a four-year contract.

About 39,000 landline and cable employees in nine states and Washington, D.C., have been on strike since mid-April.

Verizon had trained other workers to step in but there were still delays in installations for Fios customers.

Verizon said that it had high health care costs for its unionized workers, which have shrunk as it sold off large chunks of its wireline unit and focused on its mobile business, which was not unionized. It also wanted the union workers, just over one-fifth of its U.S. work force, to agree to move around to different regions when needed, which the union opposed.

The union and Verizon are not giving details of the contract, so it’s not clear yet what the agreement entails. As the number of organized workers shrinks, union fights in recent years have tended to be defensive, aimed at holding the line for their members rather than winning new benefits, said Jake Rosenfeld, sociology professor at Washington University.

The president of the Communications Workers of America union, Chris Shelton, said the agreement is a “victory for working families” and that there will be new union jobs at Verizon. Labor Secretary Thomas Perez said Friday that the agreement is being written and he expects workers back on the job next week.