President Bush this morning signed into law the most sweeping housing legislation in decades, aimed at calming rocky financial markets and giving mortgage relief to up to 400,000 homeowners.

In an unannounced White House ceremony attended by senior administration aides shortly after 7 a.m., Bush gave his imprimatur to a law he had long vowed to veto because of objections to some aspects of the legislation.

"We look forward to put in place new authorities to improve confidence and stability in markets" and to provide tougher oversight of teetering mortgage giants Fannie Mae and Freddie Mac, said White House spokesman Tony Fratto.

"The Federal Housing Administration will begin to implement new policies intended to keep more deserving American families in their homes," he added.