This May 2, 2007 file photo shows the Fannie Mae building in Washington. (AP Photo/Manuel Balce Ceneta, File)

WASHINGTON (AP) — A federal rescue of Fannie Mae and Freddie Mac could cost taxpayers $25 billion, congressional budget experts said, as the House scheduled a Wednesday vote on legislation that would tap the mortgage giants’ profits to cover any losses from saving 400,000 homeowners from foreclosure.

A costly rescue for Fannie and Freddie is just a worry, not a certainty at this point. Peter R. Orszag, director of the Congressional Budget Office, predicted in a letter to lawmakers Tuesday that there’s a better than even chance the government will not have to step in to prop up the companies by lending them money or buying stock.

The House was expected to vote Wednesday on a housing measure that would give the Treasury Department authority to throw the companies a temporary lifeline.