Local utility workers reached a tentative agreement on a new contract with NStar Friday night, avoiding a midnight deadline for negotiations and a possible strike, the workers’ union said.

After weeks of discussions, members of Utility Workers of America Local 369 had vowed to call a strike against the electric company if their contract was not settled by midnight Friday.

The two groups were at odds about health care, retirement, and life insurance benefits, as well as salary and working conditions, according to the union.

Local 369 represents thousands of workers across Massachusetts.