Union leaders and hospital management met Wednesday in a final attempt to avert the work stoppage, but no breakthrough materialized. Barring an 11th-hour agreement, the strike will begin at the start of the day Thursday.

The action is expected to cause significantly more disruption than a one-day strike in July, which was followed by a four-day lockout imposed by the hospital. That earlier job action offered a preview of the tensions now coming to a head, but the current walkout has no scheduled end date.

The dispute centers on contract terms for the nurses, who have been pressing for an agreement they say addresses staffing and working conditions at the Boston hospital. Specific details of the outstanding disagreements were not immediately available.

Hospital officials have been preparing contingency plans to maintain patient care during the strike, though the scale of the walkout — involving thousands of nurses at a major regional referral center — raises questions about how services will be affected.

The strike comes amid broader turbulence at Mass General Brigham, the hospital's parent system, which has recently announced layoffs and the closure of its only primary care clinic in Downtown Crossing. Those moves have fueled anxiety among staff and raised concerns about the system's direction.

For patients and surrounding communities, the walkout could mean postponed procedures, longer waits and reduced staffing at a hospital that serves as a critical safety net and specialty care hub for the region.

Negotiations could still resume before Thursday morning, but with no deal in hand, nurses are poised to begin the indefinite strike as planned.