The Postal Service repeated on Wednesday that without congressional action, it will default—a first in its long history, a spokesman said—on a legally required annual $5.5 billion payment, due Aug. 1, into a health-benefits fund for future retirees. Action in Congress isn't likely, as the House prepares to leave for its August recess.

The agency said a default on the payment, for 2011, wouldn't directly affect service or its ability to pay employees and suppliers. But "these ongoing liquidity issues unnecessarily undermine confidence in the viability of the Postal Service among our customers," said spokesman David Partenheimer.

The agency says it will default on its 2012 retiree health payment as well—also roughly $5.5 billion, due Sept. 30—if there is no legislative action by then.

Most everyone agrees the Postal Service needs an overhaul. It had a loss of $3.2 billion in the second quarter of this fiscal year; it is to report third-quarter results on Aug. 9. The agency blames factors including declining mail volumes and the unusual 2006 mandate by Congress that it annually set aside billions for future retirees. But while the Senate has passed legislation to overhaul the agency, the House says it doesn't expect to take up its own proposal until after August.

The two sides remain far apart. Senators voted in April, on a bipartisan basis, for legislation that largely shores up the agency's finances by returning an estimated $10.9 billion overpayment made into the federal employee pension system. The legislation limits the agency's ability to close postal branches and stop Saturday delivery.