Republicans complain that the bill is too large, contains insufficient tax cuts and is filled with spending on unnecessary projects which will not immediately create jobs.
Later on Thursday Obama decried what he described as the "petty politics" and "false theories" of the plan's critics, saying the time had come to show "leadership" over the economic crisis.
Rob Reynolds, Al Jazeera's senior Washington correspondent, said the Obama administration had gone on the offensive over the economy in recent days to counter Republican criticisms of the stimulus package, which Obama has said will create three million jobs.
The severity of the economic crisis was underlined by new figures on Thursday showing the number of US workers filing new jobless benefit claims rose to 626,000 in the last week of January - the highest level since the end of October 1982.
The US president had written earlier on Thursday in an editorial in the Washington Post newspaper that the economy was in the worst state since the Great Depression of the 1930s.
"Millions of jobs that Americans relied on just a year ago are gone - millions more of the nest eggs families worked so hard to build have vanished," Obama wrote in the newspaper.
The senate did pass one amendment to the bill on Thursday, voting to ban bonuses for top executives at banks or companies receiving taxpayer money from the previous $700bn bailout fund passed last year.
|Obama said the economy was in the worst state since the Great Depression [AFP]
On Wednesday, the senate also voted to soften a "Buy American" plan in the bill after Obama expressed concern that it could spark a trade war.
Senators approved an amendment requiring the Buy American provisions be "applied in a manner consistent with US obligations under international agreements".
The change was designed to reassure Canada, Mexico, the European Union and other major trading partners that they would be exempt from a requirement in the bill that all public works projects funded by the stimulus package use only US-made iron, steel and manufactured goods.
The House of Representatives had passed a nearly identical "Buy America" provision without such a guarantee.
The US economy is in a recession following months of market turmoil sparked by the subprime mortgage crisis, tight credit conditions and slumping global markets.