The largest nurses' strike in New York City history could begin on Monday morning if a tentative settlement isn't reached between the nurses' union and hospitals.

Nearly 16,000 nurses are threatening to walk off their jobs on Monday morning, according to the New York State Nursing Association (NYSNA), the union representing the nurses.

New York Gov. Kathy Hochul declared a state of emergency Friday in anticipation of a possible strike and appealed to the hospitals and nurses' union to hammer out a last-minute deal, saying that a strike "could jeopardize the lives of thousands of New Yorkers and patients."

"I'm strongly encouraging everyone to stay at the table, both sides, management and the nurses, until this is resolved," Hochul said.

Five privately-run major hospitals in New York City would be affected by a strike. The hospitals, according to the union, are the wealthiest in the city and include Mount Sinai Hospital, Mount Sinai Morningside, Mount Sinai West, Montefiore Einstein, and New York-Presbyterian.

The hospitals are prepared to continue offering care despite any pending work interruptions, according to officials, who said patients should not avoid or delay seeking help for any medical emergencies.

The NYSNA said during an video conference update Sunday morning that there has been no movement in the labor talks with the five hospitals, affecting more than 15,000 nurses.

The NYSNA is calling for an agreement that includes pay hikes, safe staffing levels, full health care coverage and pensions, and workplace protections against violence.

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A source familiar with the labor negotiations told ABC News that the nurses are expected walk off their jobs beginning at 6 a.m. Eastern time on Monday.

The nurses' contract, reached in 2023 after a three-day strike, expired on Dec. 31.

"We continue to bargain in good faith in the hopes of reaching an agreement that is fair, reasonable, and responsible," a spokesperson for the Mount Sinai Healthcare system said in a statement on Saturday. "While we know a strike can be disruptive, we are prepared for a strike that could last an indefinite amount of time and have taken every step to best support our patients and employees in the event NYSNA forces our nurses to walk away from the bedside for the second time in three years."

"NYSNA leadership’s reckless and irresponsible demands totaling $3.6 billion, including a nearly 40% wage increase, and taking issue with our reasonable measures like rolling out panic buttons for frontline staff in the Emergency Department, clearly put patients at risk," Joe Solmonese, senior vice president, Strategic Communications, for Montefiore Einstein hospital, said in a statement.

"We are preparing for what we anticipate could be a multi-week strike, and are resolute in devoting whatever resources are necessary to safe and seamless care for our community," the statement continued.

The impasse between the NYSNA and management of the private New York City hospitals continued even as the union announced tentative settlements last week that diverted strikes at four so-called safety-net hospitals in the New York City area.

Nurses at three major Northwell Health hospitals on New York's Long Island reached a tentative contract agreement on Thursday and called off a strike, according to the NYSNA. Nurses at Brooklyn Hospital Center and Wyckoff Heights Medical Center, and those who work for the BronxCare Health System, also rescinded strike notices when they reached a tentative contract, the NYSNA said.

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"That leaves New York City's wealthiest hospitals as the outliers who have refused to settle fair contracts that protect patients and nurses," NYSNA President Nancy Hagans said in a video statement on Saturday.

Hagans added, "Instead of guaranteeing health care for nurses, these wealthy hospitals are pushing to cut health care benefits for nurses who put their own health on the line to care for New Yorkers during this historic flu surge, the COVID-19 pandemic and everyday injuries and hospital violence."

Hagan pointed to a police-involved shooting last week at a Brooklyn hospital as the latest example of the violence hospital workers face.

On Thursday, a 62-year-old former NYPD officer, allegedly wielding a sharp object, was fatally shot by New York City police officers at New York-Presbyterian Brooklyn Methodist Hospital. The man, according to police, was shot after he allegedly barricaded himself in a room with an adult patient and a hospital security worker and threatened to hurt himself and others.

ABC News' Ahmad Hemingway and Darren Reynolds contributed to this report.