WASHINGTON — The Bush administration on Saturday formally proposed to Congress the largest financial bailout in United States history, requesting virtually unfettered sweeping authority for the Treasury to purchase up to $700 billion in mortgage-related assets from financial institutions headquartered in the United States. 

The proposal was stunning for its stark simplicity: less than three pages, it would raise the national debt ceiling to $11.3 trillion. And it would place no restrictions on the administration other than requiring semi-annual reports to Congress, allowing the Treasury to buy and resell mortgage debt as it sees fit.

Staff from the Treasury Department and the House Financial Services and Senate banking committees immediately began meeting on Capitol Hill, where negotiations are likely to be complicated but quick. Democratic Congressional leaders have pledged to help approve legislation by the end of this week.

The plan, an ambitious effort to transfer the bad debts of Wall Street into the obligations of American taxpayers was put forward by the administration late last week, after a series of bold interventions on behalf of ailing private firms seemed unlikely to prevent a crash of world financial markets.

A $700 billion expenditure on distressed mortgage-related assets is roughly what the country has spent in direct costs on the entire Iraq war and more than the Pentagon’s total yearly budget appropriation.

“It’s a big-picture package, because it’s a big problem,” President Bush said on Saturday at a news conference, after meeting with President Alvaro Uribe of Colombia. “The risk of doing nothing far outweighs the risk of the package.”

But while the administration sent over a streamlined proposal, it is unlikely to stay at just two and half pages.

Key Democratic lawmakers have made clear that they want to include at least some assurance that the administration will move aggressively to implement a program to help hundreds of thousands of troubled borrowers at risk of foreclosure.

A bill authorizing that program — and including an $800 billion increase in the national debt limit — was approved in July. But financing for it largely depended on fees paid by the nation’s two mortgage finance giants, Fannie Mae and Freddie Mac, which have now been placed into a government conservatorship.