Democrats have hailed the approval of legislation extending healthcare to an extra 32 million Americans as a historic advance in social justice.
The Speaker of the House of Representatives, Nancy Pelosi, said it was comparable to the establishment of Medicare and Social Security.
The bill was passed in the House on Sunday evening by just seven votes.
But Republicans have vowed to continue to challenge it, saying it is too expensive and promotes big government, the BBC reports.
Senator John McCain, the defeated presidential candidate, warned that outside the capital "the American people are very angry" and vowed that Republicans would try to repeal it.
President Barack Obama is expected to sign the bill as early as Tuesday, after which it will go to the Senate where Democrats hope it will be passed by a simple majority under budget reconciliation.
The BBC reports Mr Obama's long, stubborn effort to reform healthcare came to fruition after a dramatic late night in Congress.
The House approved the bill passed by the Senate on Christmas Eve by 219 votes to 212, with 34 Democrats joining Republicans in voting against it.
Victory was assured only hours before voting started, when the president agreed to a deal with conservative Democrats to reiterate in an executive order that money provided by the bill could not be used for abortions.