WASHINGTON (AP) — The nearly bankrupt U.S. Postal Service on Thursday reported a quarterly loss of $5.2 billion and warned it will miss another payment due to the Treasury, just one week after its first-ever default on a payment for future retiree health benefits.

From April to June, losses were $2.1 billion more than during the same period last year.

The mail agency said it is being hurt significantly by mounting costs for future retiree health benefits. Those expenses made up $3.1 billion of the post office's quarterly loss.