The US Postal Service says it lost $US5 billion ($A5.38 billion) over the past 12 months.

It’s the seventh straight year the agency has reported a net loss.

Postal officials say the loss increases the urgency for Congress to let them end Saturday mail delivery and reduce payments for retiree health benefits.

The Postal Service has struggled for years with declining mail volume and required payments of $US5.6 billion annually in health care costs for future retirees.

It has defaulted on three of those payments.

Revenue from package delivery continued to grow, rising eight per cent last year.

But that’s not enough to offset losses in first class mail, which has been the post office’s most profitable service.