WASHINGTON — Hours after President Bush dropped his veto threat, the House on Wednesday passed a measure to help homeowners hurt by the subprime crisis and make funds available to shore up Fannie Mae and Freddie Mac, if necessary.

The bill, which passed 272-152, would create an affordable housing fund, paid for by Fannie Mae and Freddie Mac. The fund would provide $500 million for foreclosure rescues in the first year. The measure also tightens regulations of Fannie and Freddie, the main purchasers of mortgages from credit unions. It would also create a new regulatory entity, the Federal Housing Finance Agency.

It also gives the Treasury Department the power to buy shares of Fannie and Freddie if either of those government-sponsored enterprises needs additional capital. Fannie and Freddie own or guarantee $5.2 trillion worth of home mortgages, about half of all outstanding loans. Fannie and Freddie would also be allowed to purchase loans of us much at $625,000 in high-cost parts of the nation.