President Barack Obama pressed divided lawmakers to back the legislation, his top domestic priority, promising it "will prevent a crisis" like the global meltdown of 2008 and ridiculing Republican opposition to the bill.
"It's reform that will protect our economy from the recklessness and irresponsibility of a few," the president said in remarks prepared for delivery at a rally in Racine, Wisconsin.
Senate Democratic Majority Leader Harry Reid said the upper chamber would not take up the measure before the week-long July 4 recess, amid embattled efforts to rally the 60 votes needed to ensure passage there.
The bill targets Wall Street excesses blamed for the global financial crisis of 2008, which has left US unemployment stubbornly high at nearly 10 percent four months before critical November elections to decide control of Congress.
Obama said the bill would "protect consumers against the unfair practices of credit card companies and mortgage lenders" as well as ensure "taxpayers are never again on the hook for Wall Street's mistakes."
The compromise legislation, finalized by Senate and House of Representative delegates last week after a marathon 20-hour session, marked an important victory for the Democratic president ahead of mid-term elections in November.
It creates a new consumer financial protection agency, an early-warning system to predict and prevent the next crisis, and mechanisms aimed at liquidating rather than saving companies once deemed "too big to fail."
The legislation also closes loopholes in regulations and requires greater transparency and accountability for hedge funds, mortgage brokers and payday lenders, and arcane financial instruments called derivatives.
Obama joined fellow Democrats in hammering House Republican Minority Leader John Boehner for an interview in which he assailed the bill and described it as "killing an ant with a nuclear weapon."
"That's right. He compared the financial crisis to an ant. The same financial crisis that led to the loss of nearly eight million jobs. The same crisis that cost people their homes and their lives savings," said Obama.
"Americans don't believe the financial crisis was an ant. They know that it's what led to the worst recession since the Great Depression," the president said in his prepared remarks.
"And they expect their leaders in Washington to do whatever it takes to make sure a crisis like this never happens again. The Republican leader might want to maintain a status quo on Wall Street. But we want to move America forward."
Boehner shot back that he "wasn't minimizing the crisis America faced" but "was pointing out that Washington Democrats have produced a bill that will actually kill more jobs and make the situation worse."
Obama should be focused on promoting job growth "instead of my choice of metaphors," he said in a statement.
In Congress, meanwhile, Democrats scrambled to rally the 60 votes needed to get the bill through the Senate, a special challenge after the death this week of Democratic Senator Robert Byrd.
In an unusual move, the White House's allies late Tuesday scrubbed a 19-billion-dollar bank fee from the bill in order to win over Republican Senator Scott Brown, whose support could make the difference in passage.
In a statement early Wednesday, Brown -- who had explicitly opposed the measure because of what he denounced as the "bank tax" -- welcomed the move but withheld his support and said he would "review" the bill over the July 4 break.