A union representing U.S. Postal Service workers has said the agency’s financial difficulties are “manageable” and Congress is the only thing standing in the way of solvency.

The National Association of Letter Carriers was responding to news that USPS recently hit its $15 billion borrowing limit. The union said the mandate to prefund health benefits for retirees is bankrupting the Postal Service, arguing USPS is the only government agency that has that requirement.

“As we have long acknowledged, the Postal Service does face a serious -- but quite manageable -- business problem as a result of the public’s increasing use of the Internet for email and other transactions,” NALC said in a statement.

The Postal Service itself has said prefunding health benefits for future retirees is a major cause for -- but not the only factor in -- its financial crisis. USPS’ official business plan to restore financial solvency seeks congressional action to reverse the mandate.

The union said it can use the billions of dollars going to prefunding annually to grow as Internet and e-commerce open the door to new revenues.

“There are challenges, but there are also opportunities for growth,” NALC said.

The 2006 Postal Accountability and Enhancement Act requires 10 percent of the agency’s budget go toward future retirement funds, which NALC said has prefunded the health benefits for the next 75 years.

“By mandating these payments and refusing to allow the Postal Service to access its own pension fund surplus, Congress has turned a manageable business challenge into a nightmare of artificial deadlines and unnecessary financial burdens,” the union said.

The USPS Office of Inspector General also identified a $25 billion surplus in the agency’s Federal Employee Reserve System, which the Postal Service has argued it cannot afford.

NALC said the Postal Service can refocus these surpluses to ease the agency’s fiscal woes.