Staples Inc SPLS.O said it will end a pilot program with the U.S. Postal Service to set up mini-post offices in the company's retail outlets, after several protests outside the stores.
Postal workers have protested the program for months, objecting to expanding post office services to Staples stores, staffed with non-union workers.
The news comes days after the American Postal Workers Union won the support of the American Federation of Teachers (AFT) after it approved a resolution to boycott Staples.
The AFT represents 1.6 million members in education and other fields, according to its website.
The USPS and Staples agreed in October to allow Staples employees to sell postal packaging and accept mail that is later picked up from the stores by postal workers.
The yearlong pilot program was launched in 82 Staples stores in California, Georgia, Pennsylvania and Massachusetts.
USPS spokeswoman Darleen Reid said, "The 82 store locations will be transitioned into the U.S. Postal Service's long-established Approved Shipper Program by Aug. 29."
In the pilot program, Staples sold only USPS shipping services and products. However, in the approved shipper program, Staples, like other retailers, will offer some postal agency products alongside those of other shippers.
"Staples will continue to explore and test products and services that meet our customers' needs," Carrie McElwee, a Staples spokeswoman said in an email.
In March, Staples said it would close up to 225 stores in the United States and Canada - 12 percent of its North America outlets - as it loses customers to mass market chains and e-retailers.
The Postal Service has also been plagued by financial troubles as more people pay their bills and communicate electronically instead of sending stamped mail, and as it struggles to pay into a health fund for its future retirees, as mandated by a 2006 law.
(Reporting by Devika Krishna Kumar in Bangalore; Editing by Lisa Shumaker)