The agency did not specify how long the inventory was expected to last, so it's unclear exactly when pennies will no longer be in circulation. Blanks are flat metal discs that eventually become coins,

The United States wouldn't be the first country to eliminate the coin, Turco said. Canada, for example, decided to phase out its penny in 2012. In the U.S., the Department of Defense stopped using pennies at its overseas bases in 1980 because it became too expensive to ship them.

The Treasury is phasing out production of the penny, a coin that has been in circulation for centuries, in a move that is expected to save $56 million each year.