The U.S. Postal Service will see an additional $2 billion in annual losses if Congress does not extend a temporary price hike on stamps before Sunday.

The federal agency, which does not receive federal funding, is already slated to lose $5.5 billion this year. But it would lose more if a temporary price increase on first-class stamps that was implemented two years ago by the Postal Regulatory Commission to make up for losses endured during the recession is allowed to expire April 10.

It's the first time since the creation of the postal service that the price of stamps could drop. The USPS would lose 2 cents per stamp, as the price would drop from 49 cents to 47 cents, which would add up to significant losses.

The White House is urging Congress to extend the price increase and not pass comprehensive reforms for the service.

"However, preventing these surcharges from expiring would only offer a short-term solution. Comprehensive legislative reform is needed to address the structural mis-alignment of USPS' costs and revenues," Office of Management and Budget Director Shaun Donovan wrote in a blog Thursday.

Donovan said proposed reforms in Obama's fiscal 2017 budget proposal would improve the agency's efficiency, update its business model and realign its revenues with expenses, ultimately putting the post office on a "sustainable business path," including $27 billion in cash relief, operational savings and additional revenue over the next three years.