WESTPORT — A walkout threatened by union nurses and other employees at St.Vincent’s Behavioral Health on Long Lots Road has tentatively been called off.

In a statement issued Thursday afternoon, the tentative deal was announced — after “15 hours of negotiations” — by the Connecticut Health Care Association, District 1199/NUHHCE, the union representing registered nurses and other hospital workers at the local mental healthcare facility.

The proposed settlement is subject to ratification by the union members.

The union had organized a rally outside the facility Tuesday morning, threatening to call a strike Dec. 17 against Hartford HealthCare, which now owns the former Hall-Brooke Hospital. It is the parent company of St. Vincent’s Medical Center in Bridgeport, which acquired the Westport facility several years ago.

“The two bargaining teams have been in negotiations for over seven months, but talks broke down over mandatory overtime, one of the biggest concerns of union members at the facility,” according to the union’s statement.

The mandated overtime shifts were criticized by workers who spoke at the Tuesday rally as last-minute disruptions of their personal and family lives.

Hartford HealthCare officials, like those managing other healthcare systems during the COVID-19 pandemic, have said they are facing challenges to maintain operations caused by staffing shortages.

William Jennings, president of St. Vincent’s Medical Center, said in a statement: ““St. Vincent’s Behavioral Health in Westport is pleased to have reached a mutually satisfactory agreement through good faith negotiations.”

The union statement says that after its strike threat, workers won “substantial changes to mandatory overtime language, including an hourly contractual stipend for voluntary shift pick-ups to help avoid staff being mandated. 

“Additionally, they won hourly contractual stipends for those who are mandated. The agreements also put restrictions around how, when and under what circumstances mandatory overtime can occur … CHCA members will be able to refuse two mandated overtime shifts per year without fear of discipline.”