It was the latest sign of mounting congressional pressure on James Lockhart, the director of the Federal Housing Finance Agency, to ensure that the companies use their clout in the mortgage market to help homeowners caught in the housing crisis.
The senators - Sherrod Brown of Ohio, Bob Casey of Pennsylvania, Bob Menendez of New Jersey and Charles Schumer of New York - wrote that the companies should "take whatever actions are necessary" so more families "do not have to suffer the economic and personal disaster of foreclosure."
The firms hold or guarantee some $5 trillion in outstanding mortgages, more than half the nation's total. The foreclosure freeze, which the lawmakers said should last at least 90 days, would not apply to all those loans.
The Bush administration seized control of the companies in a bid to help reverse a prolonged housing and credit crisis. /*Fannie Mae*/ and /*Freddie Mac*/ now are under a conservatorship that ultimately could cost taxpayers billions.
The administration ousted Fannie Mac chief executive Daniel Mudd and Freddie Mac chief executive Richard Syron and replaced them with Herb Allison, a former vice chairman of Merrill Lynch, and David Moffett, a former vice chairman of U.S. Bancorp, respectively.
Prominent Democrats including Massachusetts Rep. Barney Frank, chairman of the House Financial Services Committee, have made it clear they expect Fannie Mae and Freddie Mac to do more to help homeowners now.
They have called for Lockhart to follow the example of Sheila Bair, the Federal Deposit Insurance Corp. head, who has prodded banks to develop comprehensive plans for modifying loans that homeowners can no longer afford. The FDIC temporarily froze foreclosures after it took over the collapsed Pasadena, Calif.-based bank IndyMac. The agency later engineered a plan to allow most IndyMac borrowers who were seriously delinquent or in default on their mortgages to switch into loans capped at an interest rate around 6.5 percent.
Frank said this week he was "confident" the administration would push Fannie Mae and Freddie Mac to take similar action. "We will be encouraging Lockhart to do that," he said.
A spokeswoman for the housing agency said it received the letter and would respond soon.
Republicans and Democrats also are pushing Lockhart to slash the $24 million in compensation that Mudd and Syron stand to gain as they leave their posts.
Frank's committee plans a hearing next week examining how the foreclosure prevention law enacted in July is working. Frank, Democratic Sen. Chris Dodd of Connecticut, chairman of the Senate Banking, Housing and Urban Affairs Committee, and Schumer, who heads the Joint Economic Committee, all plan hearings over the next two weeks on the government's takeover of Fannie Mae and Freddie Mac.
Associated Press writer Alan Zibel contributed to this report.