WASHINGTON — As bipartisan support grows for expanding the role of a federal housing agency in response to the mortgage market crisis, the chairman of the Senate Banking Committee yesterday called on top administration officials to move quickly toward making that change.

Sen. Christopher Dodd, D-Conn., urged Treasury Secretary Henry Paulson and Housing Secretary Alphonso Jackson in a letter to "move expeditiously" with administrative changes to the Federal Housing Administration so it can be used to help struggling borrowers avoid foreclosure. The idea is to widen the mandate of the Depression-era agency, which insures mortgages for low-income borrowers, to allow it to guarantee mortgages for homeowners in default who are refinanced into higher-rate loans. The FHA cannot currently do so.

The administration is examining the possibility of such a plan for the FHA, part of the Department of Housing and Urban Development, and Paulson has asked Treasury staff to work with HUD to find ways to help troubled homeowners.

"I want to urge you to move expeditiously in this direction," Dodd wrote Paulson and Jackson. "Our nation is experiencing record foreclosures, and an unprecedented number of Americans could lose their homes. ... At such a critical time, it is essential that the FHA act effectively ... to preserve homeownership for as many Americans as possible."

Legislation being considered in Congress, meanwhile, would raise the maximum mortgage amount that FHA can insure in high-cost areas to $417,000 from the current $362,790.

Government officials and real-estate industry interests maintain that the FHA is hamstrung by existing law. The size of mortgages the agency can insure is often too small to attract borrowers in expensive areas such as California and the Northeast — reducing the FHA's share of the home mortgage market to around 4 percent from 19 percent a decade ago.

The FHA currently backs some 3.7 million home loans in the event of default.

Treasury spokeswoman Jennifer Zuccarelli declined to comment on Dodd's letter.

HUD spokesman Steve O'Halloran said the agency continues "to aggressively help creditworthy families move to a safer, fairer and more affordable loan product with FHA. ... With congressional support, the FHA can be a safe haven for even more families who want to achieve and maintain the dream of homeownership."

White House spokesman Tony Fratto said expanding the FHA's mandate is a "high priority" for President Bush.

The request by Dodd, who is a candidate for the Democratic presidential nomination, comes at a time of politically tinged debate in Washington over possible responses to the tightening of available credit in the mortgage market.

On Tuesday, Dodd held a private meeting with Paulson and Federal Reserve Chairman Ben Bernanke. He urged Bernanke to use "all the available tools at his disposal" to ensure that the credit squeeze that has been roiling global financial markets and the turbulence in the mortgage market don't undermine the U.S. economy.

Dodd told reporters Bernanke had assured him the central bank was prepared to do so.