Washington - Republican leaders have forged ahead with a health care replacement plan despite strong opposition from lawmakers within the party, highlighting the deep divisions surrounding US President Donald Trump's chief legislative priority.Two committees in the House of Representatives held marathon sessions on Wednesday to debate a sweeping bill that unwinds and replaces the Affordable Care Act, the emblematic health care reforms implemented under Barack Obama.After seven years of Republican efforts to rip up Obamacare, it remained unclear whether Trump has the necessary votes to get the increasingly controversial replacement measure across the finish line, even with Republicans controlling the White House and both chambers of Congress.Trump and his team are "in full sell mode" regarding the plan, White House press secretary Sean Spicer said.Republican leaders indicated they want to get the bill to the president's desk prior to the Easter break in early April.But the plan suffered a serious blow Wednesday when several major hospital and medical organisations, including the American Medical Association which represents more than 200 000 doctors, lined up to oppose the American Health Care Act.The "critically flawed" bill would "result in millions of Americans losing coverage and benefits" and would raise prices for the poor and sick, the association said.Tempers flared in the House Energy and Commerce Committee as lawmakers clashed over how to proceed.Democrats sought unsuccessfully to postpone the bill's consideration for 30 days. They also threatened to introduce some 100 amendments, some of which were debated on Wednesday."If people didn't like Obamacare, they're going to hate this," said House Democrat Eliot Engel.The plan was crafted by Republican leaders and endorsed by Trump, who campaigned heavily last year on a pledge to repeal and replace Obamacare.But influential Republicans are hardening against the plan, arguing it is too similar to the law despised by conservatives.Far-right lawmakers said the plan shuns conservative principles by maintaining government subsidies of the Affordable Care Act, under the guise of "refundable tax credits" for people to purchase their own health insurance."I don't think the plan they introduced yesterday is going to bring down the cost for working-class and middle-class families," House Republican Jim Jordan, who has described the tax credit provision as a new entitlement, told MSNBC.Hard sell Under pressure to bring several Republicans on board, Trump huddled with conservative leaders whose organisations have panned the plan.Among them was Adam Brandon of FreedomWorks, who described the White House meeting as "a great step" toward getting Trump and conservative groups on the same page."I'm confident in the process Obamacare will be gone and replaced with a much better alternative," Brandon said.Trump afterward dined with conservative Senator Ted Cruz, who has said the bill as written likely would not pass the Senate.Many conservatives oppose using the tax credits, which would range from $2 000 a year for someone under age 30, to $4 000 for people 60 or older.Democrats warn that those credits are on average less than the subsidies built into the Obamacare premiums.The new plan "will cause millions to lose insurance as well as blow a gigantic hole in the federal budget," top Senate Democrat Chuck Schumer said, noting that congressional officials have yet to release an estimate on the legislation's cost impact on the federal budget.Energy and Commerce Committee chairman Greg Walden promised the new plan "will not pull the rug out from anyone as we transition away from this failing law".But Democrats were adamant that repealing and replacing Obamacare would only make matters worse."Withdraw this message bill, and work with us to improve the Affordable Care Act," implored Democrat Jerry McNerney.House Speaker Paul Ryan said he had "no doubt" the bill would pass his chamber. But he acknowledged there have been "growing pains" along the way as Republicans gained control of the White House and readied their bill.Some House conservatives contradicted Ryan's positive outlook."With the current bill, there's not 218," the votes needed to pass legislation in the House, congressman David Brat told reporters.No Democrats have expressed support for the plan.With debate dragging late on Wednesday in the Ways and Means Committee, chairman Kevin Brady said the panel "will work through the night, if that's what it takes".Democrat Engel warned that Republicans' jobs would be on the line if their plan fail to improve on the current system.Should passage of Obamacare's landmark reforms lead to Democrats losing their majority in Congress, Engel told Republicans, "you guys are putting yourself in jeopardy of losing the majority because of this monstrosity".