The White House said Wednesday it wants to raise as much as $15 billion for selling off unused buildings, from warehouses and supply sheds to outdated Federal Aviation Administration towers.

The federal government has already identified 14,000 buildings and structures to sell.

The sales, which could begin in a few months, are subject to congressional approval and come at a time when the real estate market is still on shaky grounds. The White House mentioned the initiative in President Barack Obama’s fiscal 2012 budget, and said it will put a list of all available structures up on the Internet. It also plans to conduct online auctions for some of the properties…