Thousands of nurses at two New York City hospitals went on strike on Monday after contract negotiations stalled over pay and staffing levels, a move that caused one of the facilities to postpone procedures and appointments.

The walkout involves more than 7,000 nurses at Montefiore Medical Center in the Bronx and Mount Sinai Hospital in Manhattan, the New York State Nurses Association said in a statement.

The COVID-19 pandemic along with a respiratory syncytial virus outbreak and this year's flu season has put a strain on the healthcare sector across the nation's most populous city, creating tensions between nurses and their employers.

Hundreds of striking nurses Monday morning rallied outside of both hospitals where they chanted "Every patient is a VIP" as they waved signs in support of hiring more nurses and better pay.

"Enough is enough, Sinai," New York State Nurses Association President Nancy Hagan said outside of Mount Sinai on Monday surrounded by red-clad nurses. "What we are asking for is for safe staffing and quality care for patients. We don't think we are asking for too much."

The hospitals said in separate statements on Monday that they offered a 19.1% compounded wage increase to the nurses. Montefiore Medical Center also said it was committed to create over 170 new nursing positions.

"We remain committed to seamless and compassionate care, recognizing that the union leadership’s decision will spark fear and uncertainty across our community," Montefiore Medical Center said.

Montefiore said the strike forced them to reschedule all elective surgeries and procedures and postpone appointments at ambulatory locations. Sinai said most of its outpatient appointments and procedures are going forward as scheduled.

Since beginning contract negotiations four months ago, the union had been able to reach agreements or new contracts for nurses at seven other New York City hospitals.

On Sunday, nurses at Mount Sinai Morningside and West reached a tentative agreement on a new contract that included improved staffing standards and enforcement, and increased salaries over the next three years, the union said.

The union urged people who are sick to seek care, regardless of potential concerns over crossing picket lines of striking nurses.

New York City Mayor Eric Adams said on Sunday that he and his staff were closely monitoring the situation and that the city's healthcare system is prepared to meet any challenges that may arise due to the work stoppage.