Negotiators for major New York City hospital systems and the state nurses union returned to the bargaining table Friday as the city's largest nurses strike stretched into its fifth day. 

Mount Sinai Health representatives were holding bargaining sessions Friday with the New York State Nurses Association for the first time since the strike started, but Montefiore and NewYork-Presbyterian did not meet today.

"While we continue to work toward a deal, we also continue to make progress toward getting our hospitals operating at full capacity. We have extended our contracts for agency nurses to ensure we have a workforce willing to provide care to our patients. We are onboarding an additional complement of agency nurses focused on specialty areas so that we can rapidly bring our scheduled surgical volumes back to normal," Mount Sinai Health System CEO Dr. Brendan Carr said. 

"Seeing our union come together in times like these is probably of the most importance. Because we're one union, and we're strong," Mount Sinai Flushing nurse Emily Fricano said. 

"We take care of everyone. People who are sick. People who have nobody else. So why not work with us?" nurse Colleen McCormack said. 

Members of the Transit Workers Union also joined the picket line Friday. 

"Everybody said they were heroes. Everybody knows that they're frontline workers. We have a rise in flu and all types of viruses, and what do they do? They hire traveling nurses and pay three times as much. Why? They want to break the union," John Chiarello of TWU Local 100 said. 

A late-night bargaining session 

NYSNA and NewYork-Presbyterian met with a mediator for six hours Thursday night, marking the very first round of negotiations since roughly 15,000 nurses started picketing Monday, but they failed to make enough progress to reach a deal.

A nurse who told us she was at the negotiating table with NewYork-Presbyterian told CBS News New York negotiations focused on staffing and that the union cut back its demands by asking for changes to specific units. 

A hospital spokesperson said following the late-night discussions that NYSNA's proposals remained unreasonable, adding future meetings will be scheduled through a mediator. 

The striking nurses have been getting support from other city unions, including the Uniformed Firefighters Association, which represents FDNY members, who joined picket lines Thursday. 

5 hospitals involved in negotiations

NYSNA has been accusing the three hospital systems of refusing to improve staffing levels, health care benefits and workplace safety at five hospitals:

• The Mount Sinai Hospital, Manhattan
• Mount Sinai Morningside, Manhattan
• Mount Sinai West, Manhattan 
• NewYork-Presbyterian, Manhattan
• Montefiore Einstein, the Bronx.

Montefiore said it has rolled out several key programs to keep nurses safe at work, including widespread deployment of weapons detection capabilities, paying for round-the-clock armed NYPD members and issuing nurses wearable panic buttons. 

NewYork-Presbyterian also said it is committed to safe staffing and added that the hospital has the best staffing ratios in the city.  

"Unreasonable" demands, hospital says

Mount Sinai Health System said in a statement the union's proposals "would cost $1.6 billion over three years just at The Mount Sinai Hospital, raising average nurse pay to close to $250,000." 

NewYork-Presbyterian representatives have called NYSNA's demands "unreasonable."