The USPS has a $15 billion credit line, which was maxed out in late September, The Wall Street Journal reported Wednesday.
The agency's debt load grew by $2.4 billion in the third quarter, USPS spokesman David Partenheimer said.
"Being at the limit is a serious situation because our limited liquidity does not give us operating flexibility," he said. "Without passage of comprehensive legislation as part of the Postal Service's business plan to return to financial stability, we continue to project low levels of cash," he said.
Both the holiday season and the national election should give the service positive cash flow for the short term. Beyond that, Congress will have to act to solve the agency's financial problems.
On top of the $15 billion line of credit, the postal service has defaulted on $11.1 billion in retiree healthcare payments.
The financial troubles do not affect current retirees, just future retirees, the Journal said.