A health care workers union is raising concerns about the proposed merger between Southcoast Health System of New Bedford and one of Rhode Island’s biggest health care providers, saying the deal could result in higher costs and fewer jobs.

Southcoast has been discussing a merger with Care New England Health System of Providence since last fall, and the boards of both nonprofit health systems voted in May to continue those discussions.

In a letter this week, the Service Employees International Union, Local 1199, asked Attorney General Maura Healey to take a close look at the proposed transaction.

“While this merger has the potential for growth and development of health care in Southcoast communities, health care workers will remain vigilant about the merger’s effects on consumers and the regional economy,’’ Tyrék D. Lee Sr., executive vice president of the union, added in a statement. “This merger must be about expanding the delivery of high-quality, affordable health care and protecting good jobs.’’

The SEIU represents 52,000 workers in Massachusetts, including at Southcoast.

Lee said both Southcoast and Care New England “have a history of laying off workers.’’ Both companies cut jobs earlier this year.

But Southcoast said the merger has the potential to increase jobs and access to care.

“We look to our sustained growth in jobs and clinical programs over the past 20 years as a model for future possibilities and expectations,’’ spokesman Peter Cohenno said.

Southcoast and Care New England will file their plans with regulators in the next 90 days, he said.

Combined, the two organizations will create a system of eight hospitals, more than 15,000 employees, and more than $2 billion in annual revenues across two states. Keith A. Hovan, the chief of Southcoast, will become chief executive of the combined company.

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