The cash-strapped U.S. Postal Service is unloading 5 acres of vacant land on A Street in South Boston.

The 5-acre plot, part of the Postal Service’s extensive real estate holdings in Boston’s Fort Point neighborhood, was formerly used for truck storage. It’s a sizable slice of a parking lot that creates a gap in the warehouse streetscape along A Street. The lot’s sale is unrelated to the agency’s planned move from South Station to the area around the Reserved Channel waterway in South Boston, according to Postal Service spokeswoman Sue Brennan

Brennan cast the sale as part of a wider, nationwide effort to combat rapidly falling revenues. The lot is one of approximately 200 pieces of real estate nationwide that the Postal Service is either actively marketing or considering putting up for sale.

"In 2008, we had a $3-billion loss in revenue, and this year is looking exponentially worse," she said. "Nationwide, we’re looking at excess property to sell. We have not really embarked upon something like this before. We’ve never done it at this level. It’s a revenue generation opportunity for us. It’s our fiscal responsibility."

The Postal Service tried to sell the 5-acre parcel last year, but talks failed. Brennan declined to identify the party the Postal Service was negotiating with last year, saying, "The purchaser cannot be identified until a contract is signed."

Under the Boston Redevelopment Authority’s 100 Acres Planned Development Area for the neighborhood, the Postal Service’s large Fort Point lots are zoned for residential-commercial mixed use and parkland.