Negotiators from Brigham and Women’s Hospital and the union representing its 3,300 nurses again failed to reach a contract agreement Friday that would avert a planned strike, but said they would continue trying to work out a deal over the weekend.

Unless the hospital and the Massachusetts Nurses Association reach a deal, the union has threatened a one-day strike, beginning 7 a.m. Monday. Brigham plans to lock out the union nurses for an additional four days while using temporary replacement workers.

Both sides negotiated for 12 hours on Friday and said they would resume talks Saturday morning.

“Nurses will not give up this fight,’’ the union said in a statement Friday night. “Today nurses moved significantly on wages and are seeking a fair settlement. Without a fair agreement that values patients over profits, Brigham nurses are prepared to strike for 24 hours starting Monday morning.’’

Hospital officials said they remain hopeful that a strike will be avoided, but said they are continuing their “comprehensive preparedness efforts’’ to ensure that patients receive care if the walkout occurs.

The planned strike is already disrupting care at Brigham, where surgeries are being canceled and patients are being transferred in preparation for a possible walkout by a significant portion of the hospital’s workforce.

The union and Brigham, a teaching hospital owned by Partners HealthCare, disagree on wages, benefits, and staffing levels for nurses. Hospital and union officials continued their bitter exchange of public statements this week, even as negotiators made a last-ditch effort to reach a compromise.

Union officials accuse hospital leaders of “corporate greed’’ and disrespect for nurses, which led them to stage a job action. Hospital officials say the union’s demands on wages and health benefits are unaffordable.

“There is nothing we want more than to avert a strike and the disruption that would occur,’’ Brigham’s chief executive, Dr. Elizabeth G. Nabel, said at a press conference Friday.

Nabel said she was disappointed hospital-union relations have deteriorated so badly, and she questioned whether the union truly wanted to avoid a strike, given that the job action was coordinated with two other nursing strikes in Minnesota and California.

Brigham has been preparing for a strike for several days. It plans to scale operations down to 60 percent of normal and employ about 700 replacement nurses.

Brigham’s chief operating officer, Dr. Ron M. Walls, said the 793-bed hospital had 570 patients on Friday. It plans to reduce that number to 450 patients by Monday. Many patients already have been transferred to other hospitals.

Walls said Brigham would not transfer adult patients without their consent. But for babies in the newborn intensive care unit, state officials can authorize a transfer without parental consent if they believe the infants won’t be able to receive safe care at Brigham, he said. “We don’t anticipate getting to that,’’ he added.

Patients in the newborn ICU include premature babies who need tubes and machines to feed and breathe. Thirteen infants already have been transferred from the unit.

Brigham plans to reduce its surgeries from about 120 a day, to about 90 a day. Surgeons will use just 15 operating rooms, instead of the regular 42.

Hospital officials said they will not turn away patients seeking emergency care during the planned strike. All patients coming to the emergency department would be treated, they said, but those needing to be admitted may be transferred to another hospital.

Brigham leaders said they are working to ensure patients receive safe care during a strike, but the nurses union issued a statement saying its members are worried about patient safety.

“That is why Brigham nurses voted overwhelmingly for a 24-hour strike starting Monday morning,’’ the union said. “It is solely the hospital’s decision to jeopardize safe patient care with a subsequent four-day lockout.’’

The hospital and the union have been negotiating a contract for about 10 months.

Priyanka Dayal McCluskey can be reached at priyanka.mccluskey@globe.com. Follow her on Twitter @priyanka_dayal.