The United States Postal Service denied J.C. Penney Co. Inc. (JCP) - Get Report CEO Marvin Ellison's assertion made earlier this week, which was first reported by TheStreet, that it would be the one to hold back future e-commerce growth.

A USPS spokesman said in an email to TheStreet that the agency's "unrivaled network and infrastructure" will "enable" and "facilitate" e-commerce's "future growth," pointing out that its workers delivered 154 billion pieces of mail to the U.S. in 2016.

"The Postal Service continually adapts to a dynamic marketplace," the spokesman said on Friday. "We operate an extensive and integrated retail, transportation, processing and delivery network to serve residential and commercial customers."

At a Piper Jaffray conference on Wednesday, Ellison said e-commerce companies' like Amazon Inc. (AMZN) - Get Report  biggest challenge ahead is the USPS in particular, as it delivers more packages to homes in the U.S. than any other shipper.

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"Fulfillment costs are increasing dramatically because we have UPS (UPS) - Get Report , FedEx (FDX) - Get Report and USPS as the three main entities to ship and fulfill orders and they're not increasing capacity to deliver at the same rate e-commerce is growing," Ellison said.

He said this will cause a supply and demand issue "that's going to be apparent here pretty soon."

J.C. Penney's shares fell 3.4% to $4.85 at Monday's close.

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Editors' pick: Originally published June 16.