Passage of the Bill would open the way for the rescue measure to be sent to President George W. Bush's desk to be signed into law.
White House spokesman Tony Fratto told reporters the Treasury wanted to start buying the toxic debt as soon as possible but it could take weeks.
"It's a complicated thing that they'll be trying to put in place . . . I think it's at least weeks," he said.
Global market uncertainty continued yesterday before the vote.
US economic data amplified warnings that a recession is near and European Central Bank president Jean-Claude Trichet said Europe's economy was weakening, opening the door for the first interest rate cut there in five years.
The Bank of Japan said it injected 800 billion ($NZ11.7 billion) into the financial system as it tried to keep cash flowing while stock markets entered another day of losses.
It marked the 13th straight business day that the Bank of Japan had pumped money into the Tokyo market, part of efforts by the world's central banks to ensure that liquidity vital to the markets does not dry up.
Commodity prices fell and business leaders from hoteliers to car manufacturers, and in sectors as far apart as farming and mining, warned that a crisis that began with risky lending to the overheated US housing market was on the cusp of a dangerous new phase.
ABN Amro Craigs broker Peter McIntyre said the detail of the 460-page rescue document would be crucial to the way markets reacted.
He expected a short-term rally in markets when the Bill was passed and a growth in cash flowing back into investments.
Treasury secretary Henry Paulson wanted the package passed so he could consider regulation on the market and investment banks.
"I will be disappointed if this thing gets through and there is no regulation."
Any recovery would take at least two years and the US had to lead the way in restoring confidence to financial markets, Mr McIntyre said.
The surprise was how well the US dollar had held up but he believed that US investors were spooked by events overseas and had been taking cash home as fast as they could.
Most fund managers wanted to be buying shares in the current downturn but were prevented from doing so by the huge amount of redemptions by clients.
That had forced the funds to keep cash on hand to pay out to investors, rather than spending it on shares, he said.
Markets remained uncertain yesterday whether the Bill would be too late to stop an even downturn.
US markets dropped 4% while US and euro-zone government bonds soared higher in a renewed safe-haven rally.
Oil prices fell more than $US4 a barrel on the expected slow-down and the US dollar rose to a 12-month high against the euro on the speculation of a rate cut by the ECB.
Credit markets remained deeply stressed.
With banks fearful of lending to each other, direct bank borrowing from the US Federal Reserve shot to a record high, averaging a staggering $US368 billion a day.
Even if the bail-out plan passes, some are questioning whether the measure could stop more housing-related dominoes from falling in the US.
Mr McIntyre said the deal aimed to take the toxic housing assets off bank balance sheets, leaving them in isolation so no-one could reprice them.
It was hoped they would recover to par value within three years.
If they did not recover, the US Government would face a further financial crisis.
"A lot of the current events have been blamed on accountants and the introduction of the new international reporting standards, which have forced banks to write down the value of the assets.
"A lot of those assets might recover back to par but no-one knows," he said.
