The dispute with Mass General Brigham, the hospital's parent system, centers on wages, healthcare benefits, and how to address persistent staffing shortages. The strike was initially scheduled for mid-October but was postponed so nurses could consider the hospital's "final offer." Union members voted to reject that offer on Nov. 1 and set a new strike date.

Hospital leadership said Tuesday night that it is working "to ensure that we continue to provide safe, high-quality care to our patients throughout any strike, regardless of its duration." Patients should plan to attend appointments as scheduled unless they are contacted by the hospital and told otherwise, according to the hospital.

"Skilled, experienced nurses will fill in during the strike, joining our existing care teams," the hospital's website states. "Many of these nurses work at academic medical centers across the country. They will receive orientation before their first shift."

The union said earlier in the week that "some progress" had been made during bargaining, but on Wednesday morning it said it was still waiting to hear from hospital management about resuming negotiations.

"We are calling on Governor Maura Healey and Boston Mayor Michelle Wu to intervene and urge MGB leadership to return to the bargaining table TODAY," said Jim McCarthy, vice chair of the nurses union, in a statement. "MGB has the opportunity to prevent a strike that could significantly disrupt patient care. Our nurses are ready to negotiate anytime, anywhere. The question is whether MGB is willing to do the same."

The hospital said no further talks are planned, but that it has been trying to get the union to the negotiating table through a mediator without success.

"BWH remains open to continuing discussions and finding a path to agreement within the financial parameters of its last, best and final offer," hospital leadership said.

The standoff follows a one-day strike by Brigham nurses in July, after which the hospital locked them out for four additional days due to contractual obligations for temporary replacements. That action was the largest healthcare strike in state history at the time, but an open-ended strike would be far more disruptive to patients and to the region's healthcare system.

The prospect of a prolonged walkout at one of Boston's premier academic medical centers has drawn attention from elected officials and community leaders, who are watching closely for signs that the two sides might return to the table before Thursday's deadline. For patients and their families, the hospital's message is to keep appointments unless notified, while the union argues that a strike can still be averted if Mass General Brigham leadership agrees to resume negotiations.