Gov. Kathy Hochul attempted Sunday evening to avert a nurses strike at two of New York City’s largest hospitals as negotiations remain unresolved on the eve of a threatened walk-out.

Roughly 7,000 nurses across Mount Sinai Hospital and Montefiore Medical Center will now strike Monday morning, after negotiations broke down overnight. The action comes even as the union representing the nurses announced tentative agreements with two other Mount Sinai facilities earlier on Sunday.

The threat has left hospital administrators and city officials scrambling to divert ambulances and transfer patients, including newborns, away from the impacted facilities. Elective surgeries at both hospitals are currently postponed.

In a statement on Sunday night lamenting the “outstanding issues at Montefiore and Mount Sinai,” Hochul said she was “calling for binding arbitration so that all parties can swiftly reach a resolution.”

"We will continue to work with partners and all parties so that New York City hospitals and nurses can continue to play their critical role in caring for New Yorkers,” she said.

The strike was set to begin if a deal was not reached by 6 a.m. Monday. Picket lines are scheduled to run from 7 a.m. to 7 p.m.

In consecutive statements on Sunday night, leaders of both Mount Sinai and Montefiore said they were “grateful” for the governor’s suggestion, and called on the New York State Nurses Association to drop their plans to strike.

“We expect that NYSNA will now rescind its strike notice so we can continue to work on an agreement and Mount Sinai nurses can continue caring for their patients,” Kenneth L. Davis, the CEO of Mount Sinai Health System, said in a statement.

The nurses union, meanwhile, offered no indication that the governor's push for arbitration would be enough to avoid a potential strike.

"Gov. Hochul should listen to frontline COVID nurse heroes and respect our federally-protected labor and collective bargaining rights," NYSNA said in a statement on Sunday night. "Nurses don’t want to strike. Bosses have pushed us to strike by refusing to seriously consider our proposals to address the desperate crisis of unsafe staffing that harms our patients."

Early Monday morning, Mount Sinai tweeted that NYSNA leaders had walked out of negotiations shortly after 1 a.m.

In recent days, the nurses union has announced tentative agreements with several hospitals, including Mount Sinai West and Mount Sinai Morningside on Sunday. The deal would lead to an 18% wage increase over three years, along with improved staffing ratios, according to the union.

But while nurses at Mount Sinai Hospital and Montefiore have received similar compensation offers, deals had yet to be reached as of Sunday evening.

At a press conference on Sunday, NYSNA President Nancy Hagans said the nurses were holding out for a deal that would improve care for patients, as well as staff.

“We have said our number one issue is the crisis of chronic understaffing that harms patient care,” she said.

Frances Cartwright, the chief nursing officer at Mount Sinai Hospital, acknowledged the hospital had dealt with severe staffing issues in recent years. But she told Gothamist on Sunday she remained confused why a deal hadn’t been reached for the 3,500 nurses at Mount Sinai.

“If you have all of these hospitals all agreeing to the same salary, which is very generous, which truly gives the message in a demonstrable way that we respect our nurses, I’d have to ask that question: why are we not?”

This story has been updated with additional comment from the NYSNA.