King Kullen has closed an “underperforming” grocery store and plans to shutter two more by late September while the retailer continues the process of being bought by Stop & Shop.

Bethpage-based King Kullen Grocery Co. closed its Mt. Sinai store June 20 and will close its Lake Ronkonkoma location Aug. 22 and North Babylon store Sept. 26, spokesman Lloyd Singer said.

“These stores were underperforming and the decision was made to close rather than renew leases that were coming due,” he said.

Employees are being reassigned to other stores and no layoffs are planned, he said.

While there will be no layoffs related to the three closings, some of the part-time employees will quit rather than travel to other King Kullen stores that are farther away, said Tony Speelman, president of Local 1500 of the United Food and Commercial Workers in Westbury.

Local 1500 represents about 2,700 employees in the King Kullen chain and its sister stores, Wild by Nature natural food shops, including deli staff, produce workers and cashiers. UFCW Local 342 in Mineola represents about 300 employees in King Kullen’s and Wild by Nature’s meat and seafood departments, union officials said.

Of the King Kullen workers who are members of Local 1500, 62 were at the Mt. Sinai store, 60 work in North Babylon and 52 work in the Lake Ronkonkoma location, Speelman said.

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Of those who belong to Local 342, four were at King Kullen’s Mt. Sinai store, nine work in the North Babylon location and five are in the Lake Ronkonkoma store, said Kelly Egan, executive director of field operations for Local 342.

The 32,994-square-foot Lake Ronkonkoma store, at 153 Ronkonkoma Ave., is the oldest of the stores, having opened in 1971. The North Babylon location, at 1170 Deer Park Ave., opened in 1979 and is 39,241 square feet, while the Mt. Sinai store, at 5507-200 Nesconset Hwy., opened in 1989 and was 45,409 square feet.

The North Babylon store would have faced more close competition next year, since discount grocer Aldi plans to open a store on Deer Park Avenue half a mile away by spring.

In Lake Ronkonkoma, Stop & Shop has a store at 425 Portion Road, about a mile from the closing King Kullen.

The closest Stop & Shop to the closed King Kullen store in Mt. Sinai is 2.8 miles away in Miller Place.

Founded in Queens in 1930, the King Kullen business is in the process of being sold to Quincy, Massachusetts-based Stop & Shop.

In January, Stop & Shop said it would buy King Kullen Grocery Co.’s 37 stores — 32 King Kullen supermarkets and five Wild by Nature natural food stores — all on Long Island.

Stop & Shop is owned by Ahold Delhaize, a Dutch retailer whose other grocery stores include Food Lion, Giant Food and Hannaford. Ahold also owns Peapod, the online grocery retailer.

The King Kullen deal initially was to be finalized in the first quarter of this year, and then was pushed back to the second quarter, Stop & Shop said.

“The dates were estimations. Stop & Shop continues to work through customary closing conditions and regulatory approvals relative to its acquisition of King Kullen Grocery Co., and the transaction has not yet closed,” said Stefanie Shuman, spokeswoman for Stop & Shop.

Stop & Shop declined to comment on the King Kullen store closings.

King Kullen has closed more stores than it has opened in recent years. It shut five stores between 2015 and 2017: in Selden, Syosset, Commack, Northport and East Setauket. King Kullen opened a store in a former Waldbaum’s space in North Patchogue in 2015.