At 7 a.m. this morning with no members of Congress present, President Bush signed one of the most sweeping financial legislations since the New Deal:

The law authorizes the Treasury to rescue the mortgage finance giants, Fannie Mae and Freddie Mac, should they verge on collapse, potentially by spending tens of billions in federal monies. Together, the companies own or guarantee nearly half of the nation's $12 trillion in mortgages.

Partly to accommodate the rescue plan for the mortgage companies, the bill raises the national debt ceiling to $10.6 trillion, an increase of $800 billion. The bill also creates significant liabilities and risks for taxpayers, that are virtually impossible to calculate.

"We look forward to put in place new authorities to improve confidence and stability in markets, and to provide better oversight for Fannie Mae and Freddie Mac," Mr. Fratto said. "The Federal Housing Administration will begin to implement new policies intended to keep more deserving American families in their homes."

A half-dozen top advisers to the president, including the Treasury secretary, Henry M. Paulson Jr., who was the leading advocate of the legislation in the administration attended the signing. But it was not a particularly auspicious occasion given the precarious state of the nation's financial system, and the pressure that Mr. Bush came under to sign a bill that contained provisions he had opposed.