NEEDHAM, Mass. (AP) – Shaw’s Supermarkets continued negotiations Saturday with the union representing more than 6,000 workers in Massachusetts, Rhode Island and Maine working under a contract that expires today.

A company health care plan was the key sticking point in talks between the supermarket chain and the United Food and Commercial Workers Local 791, both sides said.

The union scheduled meetings of mebers Sunday to vote on any agreement that emerges from the talks and possibly authorize a strike, union spokesman Peter Derouen said.

The union issued a counterproposal to the company’s three-year contract offer Saturday morning and was awaiting a response, Derouen said.

Terry Donilon, a spokesman for West Bridgewater-based Shaw’s, characterized the talks as “professional” and said negotiations could continue through the night and into early Sunday.

The contract expires at midnight, but the two sides could agree to an extension.

The negotiations cover workers at 39 Shaw’s stores in southeastern Massachusetts and Rhode Island and about 350 workers at a distribution center in Wells, Maine.

The talks that have been under way since June have stalled over Shaw’s offer on health care that would expand the number of plans employees could choose from with the addition of coverage through Blue Cross Blue Shield.

But the union said the plan would result in a 27 percent reduction in benefits, and shift thousands of dollars to employee insurance co-pays without increasing wages.

Shaw’s said it was offering union members the same medical plans offered to most employees at the stores not represented by Local 791.

Shaw’s, owned by Boise, Idaho-based Albertsons Inc., one of the nation’s largest food and drug retailers, says its costs for the union’s health care plan for the 39 stores have risen more than 60 percent in the last three years.