Senior Obama administration officials said Friday that a nationwide moratorium on foreclosure sales may be inevitable, despite their grave reservations about the impact a broad freeze would have on the nation's housing market and economic recovery.

Their remarks were made as pressure for a nationwide moratorium mounted Friday when Bank of America, the nation's largest bank, halted foreclosure sales in all 50 states. Senate Majority Leader Harry M. Reid (D-Nev.), who is locked in a tight reelection campaign, called on other major lenders to follow suit.

The White House has so far resisted joining the election-season calls for action but convened two interagency meetings this week to discuss reports that banks filed fraudulent documents to evict delinquent borrowers and to deal with questions about whether banks are seizing properties without having clear ownership of the mortgages.

One meeting was made up mostly of groups that regulate the housing industry, including the Department of Housing and Urban Development, the Treasury Department and the White House. The other, which involved the U.S. Securities and Exchange Commission, the Internal Revenue Service and U.S. attorneys from across the country, was focused on the question of whether financial fraud was committed.

With foreclosed properties comprising one in every four homes sold in the United States, the spreading moratorium could disrupt real estate deals in progress, slow down the process of clearing the backlog of troubled home loans and prolong the economic recovery, analysts said.

A freeze would also strike at the financial sector, just two years after it suffered one of the worst crises in its history. One government official who has been in discussions with several big financial firms said the banks are bracing themselves for a wave of lawsuits from homeowners who are fighting to keep their homes and from investors who had bought mortgage loans on Wall Street. On Friday, while the Dow Jones industrial average crossed 11,000, most major bank stocks fell.

Bank of America is the first bank to put a moratorium on foreclosures in all states, extending its suspension to states such as California and Nevada, which have been hit hardest by the housing bust. Previously, Bank of America, J.P. Morgan Chase and others had announced that they were stopping foreclosures only in the 23 states where a court order is needed for an eviction.

Industry sources said J.P. Morgan Chase, the nation's second largest bank, will expand its freeze to a handful of other states. PNC Financial Services has stopped some foreclosure proceedings, according to an industry lobbyist and a title insurance company. A PNC spokesman, Frederick Solomon, declined to comment on whether the lender was halting foreclosures. He said the bank was reviewing its procedures.

Speaking at the National Press Club, Bank of America chief executive Brian Moynihan played down the gravity of its moratorium and the impact of the paperwork flap. "We haven't found any foreclosure problems," he said. "What we're trying to do is clear the air and say we'll go back and check our work one more time."

A White House official said the administration is "very closely" monitoring the foreclosure issues and expects "lenders and servicers to follow the law and to fix any problems in their processes related to foreclosures."

Also Friday, the Federal Housing Administration said it had asked agency-approved mortgage servicers - which includes the nation's largest banks - to immediately audit their foreclosure operations. The FHA can impose financial penalties on companies that do not follow rules set by housing regulators.

Questions over the legal standing of banks in foreclosure proceedings as well as reports that these firms cut corners as they pushed foreclosures through the legal system fueled calls in Congress for a nationwide freeze and federal investigations.