Markets have seen huge volatility recently
Doubts over the speed at which the US financial bail-out plan can be introduced have emerged from both Democrats and Republicans.
Contentious issues include limiting compensation for bosses of rescued firms and wider help for Americans who could lose their homes.
Lawmakers from both sides say they need more time for debate, but a leading Democrat said progress was being made.
The White House says Congress must back the plan to prevent more economic harm.
President George W Bush said the world was watching to see if "we can act quickly to shore up our markets".
Details of the $700bn (£382bn) package are still being worked out.
Meetings took place over the weekend between Federal Reserve head Ben Bernanke, US Treasury Secretary Henry Paulson and members of Congress to try to seek consensus on the plan.
However uncertainty over how the programme will work caused the Dow Jones share index to fall by more than 370 points, or 3.27%, wiping out the gains made during Friday's rally.
'Unreasonable' expectation
Lawmakers from both sides have raised a number of concerns with the bail-out plan.
Democratic Congressman Barney Frank, chairman of the House Financial Services Committee, said Democrats would want certain changes, such as guaranteeing that the pay for bosses of the firms being bailed out was limited.
