(The Center Square) — Thousands of nurses at several major New York City medical centers went on strike Monday after contract negotiations between union leaders and the hospitals broke down over the weekend.

The New York State Nurses Association, which represents 15,000 unionized nurses at Mount Sinai, Montefiore and NewYork-Presbyterian hospitals, hit the picket lines shortly after 6 a.m. after union leaders say talks with hospital officials failed to make “meaningful progress” on core demands ranging from improved pay and health care benefits to staffing levels and workplace violence protections.