From January to March, losses were $1 billion more than during the same period in 2010.
Postmaster General Patrick Donahoe says the mail agency is incurring significant losses because Congress has failed to pass legislation allowing it to eliminate Saturday mail delivery and reduce health and other labor costs.
The Postal Service warned that its cash flow is running low. Without legislative action, the agency says it will be forced to default on more than $11 billion in health prepayments due to the Treasury this fall.
