The head of a local union representing workers at a Giant Food warehouse in Maryland said the operator gave verbal notice of plans to close the site, a move that endangers more than 400 jobs.

The area’s largest supermarket chain agreed in April to have Jessup Logistics, an affiliate of C&S Wholesale Grocers, assume operations of its dry-groceries warehouse in Jessup starting Sunday. This month, the operator began meeting with Teamsters Local 730, representing 430 workers there, to negotiate the contract set to expire May 14.

Union president Ritchie Brooks said that Tuesday, officials from Jessup Logistics informed him that the plant would shutter.

“We knew this was coming,” Brooks said. “We give them our whole list of proposals . . . they’ve come with one proposal.”

Jessup Logistics would not confirm or deny intentions to close the plant. But Bryan Granger, a company spokesman, said that it has not filed the 60-day notice of closure required under the federal Worker Adjustment and Retraining Notification Act. More negotiation sessions are scheduled in the coming weeks.

Granger said in a statement that the firm has the “responsibility to secure significant cost-savings in order to deliver groceries and products to store shelves as efficiently as possible.” He added: “There have been great advances in automation and technology in grocery distribution, which could save at least $26 million per year.”

When asked how they would hit that objective at the warehouse, Granger said: “That detail is solely between Jessup Logistics and the local at this time.”

Brooks said that he suspected the firm would close the plant and move operations to Pennsylvania, because of their reputation for taking such actions. The company shut six food distribution centers in New Jersey last month, costing 1,000 workers their jobs.

When Giant struck the outsourcing deal last year, it gave workers a choice of working for Jessup Logistics under the same contract or taking a lump-sum buyout of $50,000. More than 70 workers took the buyout, which Giant said was paid in September.

Giant, owned by Dutch conglomerate Royal Ahold, has no involvement in contract negotiations between Jessup Logistics and the union, company spokesman Jamie Miller said.

“Carl Schlicker, who runs Ahold USA now, is very anti-union . . . and C&S is doing all of their dirty work,” Brooks said.

Giant is also negotiating a contract with Local 730, along with Teamsters Local 639 representing drivers, for its produce warehouse in Jessup. The supermarket is considering transferring that facility to Jessup Logistics.

Giant closed three distribution centers in 2005 and cut 500 employees. The company has since merged much of its administrative functions with sister company Stop & Shop in Quincy, Mass.