BOSTON (AP) – Union locals representing 43,000 Stop & Shop supermarket workers in southern New England are scheduled to vote Sunday on whether to approve a new three-year contract, possibly without endorsement by union leaders, or go on strike.

Negotiations between the Quincy-based grocery chain and the United Food and Commercial Workers continued Friday without resolution over issues including health care contributions, pensions and wages.

If union leaders fail to reach an agreement with the company by Sunday, rank-and-file members of the five locals would vote on the company’s latest offer. Balloting is to be conducted in the morning and afternoon at separate locations in Massachusetts, Connecticut and Rhode Island.

“We’re either going to have a package to recommend to the members, or we’ll recommend against the company’s offer and for a strike,” Rick Charette, president of Local 1445, said during a break in negotiations held Friday in Providence, R.I.

“We’re talking more than ever before, but we’ll wait and see whether that means anything at the end of the day,” Charette said.

Stop & Shop spokesman Robert Keane said the company “remains committed to the collective bargaining process, and we hope to reach an agreement soon.”

Members of all five union locals last month authorized leaders to call a strike if necessary. The timing of any walkout is uncertain, and would be decided after Sunday’s voting.

Stop & Shop, owned by the Dutch conglomerate Royal Ahold NV, is negotiating with the UFCW’s Local 1445, covering workers in eastern and central Massachusetts; Local 328, covering Rhode Island and southeastern Massachusetts; Local 1459, covering western Massachusetts; and two units representing Connecticut workers, locals 371 and 919.

The locals are negotiating as a group in talks that began in mid-December covering workers at 231 stores. Stop & Shop workers in New York, New Jersey and New Hampshire are covered under separate contracts.

A previous three-year labor contract expired Feb. 17, and employees have since remained on the job under terms of that agreement.

Last month, Stop & Shop began placing advertisements in newspapers saying it was opening hiring centers to recruit potential temporary workers.

“Because the union has taken strike authorization votes, in case an agreement is not reached we owe it to our customers to be prepared,” Keane said Friday.

He declined to say how many temporary workers the company had lined up.

Charette, of Local 1445, said the union “will have picket lines at every store” if a strike is called.

If there is a strike, Stop & Shop might benefit by the fact that the majority of its workers are part-time employees, said David Cadden, a management professor at Quinnipiac University. Those workers would have less to lose by crossing a picket line and returning to the job than full-timers, Cadden said.

“I imagine many would be crossing the lines,” Cadden said. “They have no intention of having a career there.”

Under such a scenario, Stop & Shop might be able to maintain most of its operations, with the exception of meat counters and produce buying, areas which rely largely on full-time workers, Cadden said.

Stop & Shop currently covers 100 percent of its union employees’ health care premiums, although employees cover co-payments and deductibles. In the current negotiations, the company wants employees to cover a portion of the premiums.

The union also objects to the company’s plan to begin switching new hires from a defined benefit pension plan to an employee-funded 401(k) plan. The union says the 401(k) plan offers less financial security.