Washington ? The Bush administration insisted Sunday that Congress must move quickly to approve what one lawmaker called the “mother of all bailouts” – a $700 billion proposal to buy a mountain of bad mortgage debt in an effort to unfreeze the nation’s credit markets.

Congressional leaders endorsed the plan’s main thrust, saying passage might occur in a matter of days. But they said it must be expanded to include help for people on Main Street as well as the big Wall Street financial firms who have lost billions of dollars through their bad investment decisions. Some Democrats have also suggested capping compensation of executives at firms who get the bailout help.

Treasury Secretary Henry Paulson stressed that time was critical to get the proposal passed and that changes to the administration’s measure, which was sent to lawmakers on Saturday, could delay that approval, further unsettling global financial markets.

In yet another indication of how quickly events are moving, the Federal Reserve announced late Sunday that it had granted a request by Goldman Sachs and Morgan Stanley, the country’s last two major independent investment banks, to change their status to bank holding companies. The change will allow the two institutions to open commercial banking subsidiaries, greatly bolstering the resources of both institutions.

In the past two weeks, the government has taken over the country’s two biggest mortgage companies, Fannie Mae and Freddie Mac, and its biggest insurance company, American International Group Inc., and stood by while the nation’s fourth-largest investment bank, Lehman Brothers, declared bankruptcy and Merrill Lynch was forced to sell itself to Bank of America.

The plan the administration has developed would have the government buy up to $700 billion of the bad loans, taking them off the books of financial firms. Sen. Richard Shelby of Alabama, the top Republican on the Senate Banking Committee, said the effort would be the “mother of all bailouts” that could well cost $1 trillion with the cost of the takeovers of Fannie, Freddie and AIG included.