U.S. Postmaster General Patrick Donahoe is warning that the centuries-old agency could shut down next year if Congress does not allow it to restructure.

Donahoe told a Senate committee Tuesday that the post office is on the brink of default. He said action is needed by the end of the month or it will default on its $5.5 billion in health benefits for retired workers.

Donahoe said he is not looking for a government handout — just permission from Congress to make changes in the way the postal service operates. Among the cost-saving measures it is considering are closing unprofitable post offices and eliminating Saturday delivery.

The U.S. Postal Service gets no federal funding. It is an independent federal agency responsible for its own revenue.

The post office is losing billions of dollars as many customers turn to e-mail to send messages and letters.

But it still handles more than half-a-billion pieces of mail a day and its operations pre-date the U.S. Declaration of Independence. Benjamin Franklin was the first Postmaster General

U.S. Senator Joseph Lieberman said Tuesday that the post office is not a 18th century relic, but a 21st century asset.