US President Donald Trump has vowed to "finish off" Barack Obama's signature health care law, predicting an "unbelievable victory" after his reform passed the Republican-controlled House of Representatives.
"It's dead, it's essentially dead," Trump said, describing Obamacare as "a catastrophe."
"We're going to finish it off and we're going to go on to a lot of other things," Trump said, as the Republican health care bill now heads to the Senate where it faces substantial opposition.
Following weeks of in-party feuding and mounting pressure from the White House, lawmakers voted 217 to 213 to pass a bill dismantling much of Barack Obama's Affordable Care Act and allowing US states to opt out of many of the law's key health benefit guarantees.
Some 20 Republicans voted in opposition, along with all Democrats, in the most contentious congressional vote of Trump's young presidency.
Eyeing a victory, a jubilant Trump tweeted during the vote that, if successful, Republicans would gather for "big press conference at the beautiful Rose Garden of the White House" immediately afterwards.
The bill's passage is a conservative dream seven years in the making: doing away with a reform which Republicans accuse of sending health premiums soaring while reducing options for millions of Americans.
Watch: Democrats sing 'goodbye' on house floor
An earlier version of the plan to repeal Obamacare collapsed in March, torpedoed by opposition from both moderates and conservatives in the Republican party - and dealing the president one of the most stinging setbacks since he took office.
In extraordinary scenes in the House chamber, Republicans clapped and cheered while Democrats shouted their disapproval.
"We can continue with the status quo or we can put this collapsing law behind us. End this failed experiment," House Speaker Paul Ryan declared on the House floor.
"This bill delivers on the promises that we have made to the American people," Ryan said, referring to the relentless campaign pledges by most Republicans, including Trump last year, to do everything they could to repeal and replace the reforms that came into law in 2010.
"A lot of us have been waiting seven years to cast this vote," added.
President Donald Trump, accompanied by GOP House members, speaks in the Rose Garden of the White House in Washington, Thursday, May 4, 2017 Source: AAP
Uphill battle in the Senate
Republican leadership endured strong criticism from Democrats and several Republicans for rushing the legislation through without extended debate.
The measure now heads to the US Senate, where it faces an uphill battle.
"Where's the score?" Democrats hollered, referring to the lack of a budget office estimate of the legislation's cost for the federal government.
Republicans including Trump had campaigned relentlessly on the pledge to dismantle the 2010 reforms.
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Democrats counter that Obamacare, as it is known, helped 20 million Americans gain health coverage and saved thousands of lives by barring insurers from denying policies to people with pre-existing conditions.
The American Medical Association issued a scathing rebuke of the latest Republican effort, warning that it would lead millions of Americans to lose their health care.
The Republican party leadership apparently won over enough skeptical members with an amendment that adds $8 billion over five years to help cover insurance costs for people with pre-existing conditions.
Several medical experts and health groups publicly ridiculed the amendment, saying it falls woefully short of the hundreds of billions of dollars likely needed to help control health costs for the sick under the new bill.
