Stop & Shop workers went out on strike Thursday afternoon, frustrated by contract negotiations they say have stalled.

Union members said the strike will go on as long as it takes to get a contract they can accept. Some stores reopened Thursday staffed by management.

Five New England United Food & Commercial Workers locals representing over 30,000 Stop & Shop workers have been without a contract since late February.

Paula Zelisko of Chicopee said she knows the strike will mean lost wages and hardship for her family.

“But it’s short-term pain for long-term gain,” she said. “We need to protect our rights. We need to fight back.”

She and her co-workers are worried that Stop & Shop’s most recent offers hurt their pension plan and health benefits.

The most recent Stop & Shop proposal cuts the monthly pension benefit for many newly hired full-time employees by 32 %.

“And their raises won’t even cover the increase in the cost of living,” she said.

She’s worked for Stop & Shop for 35 years and is currently a file clerk, keeping track of price changes.

Stop & Shop’s most recent proposal would also require the average full-time employee to pay an additional $893 and the average part-time employee with employee-only coverage to pay an additional $603 in weekly health care premiums over three years.

Kristen Johnson, a 12-year Stop & Shop employee said she is hoping the strike will lead to a quick contract.

“But we are prepared to be out here for the long haul,” Johnson, who works as a deli manager at he Somerville store. "As long as it takes."

She spoke by phone Thursday from a picket line outside the store.

“Every contract year we have given back and given back. We have given back things that we have earned,” she said. “It has to stop.”

The doors to the Stop & Shop in Chicopee were closed early Thursday afternoon as workers picketed outside. There were reports on social media of closed Stop & Shops from Westfield to Boston, though others remained open.

“Given that negotiations with assistance of the federal mediators are continuing, we are disappointed that the UFCW chose to order a work stoppage in an attempt to disrupt service at our stores. Stop & Shop has contingency plans in place to minimize disruption,” the supermarket chain said in a statement on its website.

At the Stop & Shop in West Springfield, the supermarket reopened two hours after the strike was called with management as the only staff. Some customers left in frustration when they found they could not utilize all services, such as freshly sliced deli meat.

Springfield-headquartered United Food & Commercial Workers Local 1459 represents about 1,300 workers, including those in Chicopee. A recorded message on its the phone told workers to report to picket lines. Those at work were told to leave their posts and go to picket lines.

UFCW claims Stop & Shop is proposing a bad deal for workers that would cut current benefits, including health and welfare and pension plans, replace Sunday time-and-a-half pay with a smaller wage premium and cut paid holidays, vacations and sick days for new hires.

The union says the company has proposed bonuses in lieu of cost-of-living wage increases, according to a union news release.

Stop & Shop has maintained that being the only New England supermarket chain with a unionized work force has put it at a competitive disadvantage.

Stop & Shop said virtually alone among New England supermarkets in providing a majority of its associates a defined benefit pension

In a posting on its website. Stop & Shop said it has proposed a “good and reasonable offer to our union locals” that includes:

Across-the-board pay increases for all associates – no one’s pay would be cut;

Continued “Gold Level” health care benefits for eligible associates – at a fraction of what employees at other retail companies pay and with no changes to already unusually low deductibles; and

Increased company contributions to the UFCW’s defined benefit pension fund for current full- and vested part-time associates – a rare benefit in the New England food retail industry.

Stop & Shop is offering raises for Local 1459 members of $20 a week for full time hires who were on the job before April 2016 and a $1,000 bonus for those hired after that point. Part-time workers are offered raises of from 25 cents to 40 cents an hour.

The raise offers vary based on local. Local 1459 is in Western Massachusetts.

The union noted in a statement that Stop & Shop’s parent company, the Netherlands-based Ahold Delhaize, witnessed more than $2 billion in profit last year and received a $225 million tax cut from the federal government in 2017.

While Stop & Shop continues to propose drastic cuts in worker benefits, Ahold shareholders voted on April 10 to give themselves an 11.1 percent raise in dividends over last year. The expected payout on April 25 is expected to be about $880 million.

“They are a very profitable company, they made billions last year in sales and profits, and they’re trying to destroy the health benefits and pensions of our hardworking members,” said Jeff Bollen, president of UFCW, Local 1445 in Deham, in a video posted on Facebook.