The union, which represents more than 4,000 nurses at the hospital, issued a 10-day strike notice last week after members voted overwhelmingly to authorize the walkout. The renewed strike threat follows a previous round of negotiations in which nurses rejected the hospital's contract offer.

The dispute centers on staffing levels, pay, and benefits, though specific details of the latest offer were not immediately available. Union leaders have argued that chronic understaffing has jeopardized patient safety and driven experienced nurses from the bedside.

Former U.S. Senator and Secretary of State John Kerry, a longtime Boston resident, joined nurses and supporters on the picket line outside The 'Quin House in Back Bay on Sunday, lending his voice to the growing chorus of public officials backing the nurses' cause.

The strike would be the second major labor action by Brigham nurses in recent years, and it comes amid a wave of labor organizing across the health care sector nationally. If no agreement is reached by Thursday, it would be the latest in a series of high-profile strikes by nurses and other health care workers demanding better working conditions and patient-care standards.

Hospital officials have said they are committed to reaching a fair agreement and have contingency plans in place to maintain patient care in the event of a strike. The negotiations are set to begin Monday morning.