About 15,000 nurses went on strike Monday at three hospital systems in New York City, following failed negotiations over the weekend, according to the New York State Nurses Association.

The strikes are occurring at The Mount Sinai Hospital and two of its satellite campuses, along with NewYork-Presbyterian and Montefiore Medical Center in the Bronx, The Associated Press reported.

The hospitals have been hiring temporary nurses during the walkout, saying in a statement during negotiations that they would “do whatever is necessary to minimize disruptions.” Montefiore assured patients in a message that appointments would be kept.

The hospitals are negotiating with the union independently, as several other hospitals across the city and in its suburbs reached deals in recent days to avert possible strikes.

While the union has different demands at each hospital, the major issues include staffing levels and workplace safety. The union said that hospitals have given nurses unmanageable workloads.

Additionally, nurses are asking for better security measures in the workplace, citing incidents like one last week when a man with a sharp object barricaded himself in a Brooklyn hospital room and was killed by police. The union is also demanding limitations on hospitals’ use of artificial intelligence.

The nonprofit hospitals involved in the negotiations said they have been working to improve staffing levels, but that the union’s demands overall are too costly.

The last major nursing strike in the city was in 2023, at Mount Sinai and Montefiore, and lasted three days.