WRAPUP 4-GSE rescue gets big price tag; House vote looms

* Administration plan could cost taxpayers $25 billion

* U.S. home prices down again in May

* Bill due on House floor Wednesday (Adds elements of House bill, paragraphs 11-12)

By Kevin Drawbaugh and Richard Cowan

WASHINGTON, July 22 (Reuters) - A Bush administration plan to bolster Fannie Mae (FNM.N: Quote, Profile, Research, Stock Buzz) and Freddie Mac (FRE.N: Quote, Profile, Research, Stock Buzz) could cost U.S. taxpayers $25 billion, congressional analysts said on Tuesday in a report that triggered debate as Congress moved toward approving a major housing market rescue package.

Fannie and Freddie shares fell sharply on the report's release but later recovered, with Freddie stock ending higher and Fannie paring its losses.

Investors are concerned whether the two government-sponsored mortgage finance giants, which own or guarantee almost half of the nation's $12 trillion in outstanding residential mortgage debt and play an increasingly key role in the troubled American housing market, can weather a national housing slump.

New data on Tuesday showed home prices fell again in May, while Treasury Secretary Henry Paulson used a speech in New York and television interviews to push for passage of the plan as a way to restore financial stability to the markets.

"Now more than ever, we need Fannie and Freddie out there, financing mortgages," said Paulson, who wants to give Fannie and Freddie access -- if they need it -- to cheap, government capital in the form of loans and possible equity investments by the government.