President Bush has signed a massive housing bill intended to provide mortgage relief for 400,000 struggling homeowners and stabilize financial markets.

A White House spokesman said Bush signed the measure Wednesday to "improve confidence and stability in markets and to provide better oversight of Fannie Mae and Freddie Mac."

The measure, regarded as the most significant housing legislation in decades, lets homeowners who cannot afford their payments refinance into more affordable government-backed loans rather than losing their homes.

It offers a temporary financial lifeline to troubled mortgage companies Fannie Mae and Freddie Mac and tightens controls over the two government-sponsored businesses.