Washington - US House Republicans unveiled long-awaited legislation on Monday that would repeal and replace the health care reforms known as Obamacare, largely under the framework that President Donald Trump laid out in his recent congressional address.The American Health Care Act would dismantle several of the core aspects of the reforms, including ending related subsidies and taxes. It would also end the requirement for individuals to have insurance, instead providing incentives for people to purchase it on the open market."After years of Obamacare's broken promises, House Republicans today took an important step," House Energy and Commerce Committee Chairman Greg Walden said in a statement."Simply put, we have a Better Way to deliver solutions that put patients - not bureaucrats - first, and we are moving forward united in our efforts to rescue the American people from the mess Obamacare has created."Top priorityObamacare has stirred controversy since becoming law in 2010 under president Barack Obama and a Congress controlled by Democrats. But it has increased in popularity and is credited with helping 20 million Americans acquire coverage.Republicans argue, however, that insurance premiums have soared for millions of Americans, and that Obamacare has been a job killer.The new bill would preserve two popular Obamacare elements: prohibiting health insurers from denying coverage to people with pre-existing conditions, and allowing dependents to remain on their parents' plans until age 26.Republicans have not provided a cost figure for the new plan, or estimates on how many people might be covered.The legislation requires passage by the House of Representatives and Senate before it goes to Trump for his signature.Trump has declared repeal and replacement of Obamacare as his top legislative priority.Democrats blast billThe replacement plan has courted controversy for months from within Trump's own party, as some GOP lawmakers warn that the tax credits in the new measure are just a reworked version of Obamacare's existing subsidies.Under the new bill, Americans would receive such tax credits amounting to between $2 000 and $14 000 per year that would help low- and middle-income families gain access to health insurance.Several Republican governors who expanded the low-income Medicaid program through Obamacare warn that the plan could leave their state budgets underwater.The new bill ends the Medicaid expansion, opting instead for a block grant system that allows states to use the funding in ways they see fit.The first public congressional review of the legislation occurs on Wednesday, when the House Ways and Means Committee and House Energy and Commerce Committee gather to debate and amend the bill.Trump's party controls both chambers of Congress, but it holds the Senate by a 52-48 margin, meaning three or more Republican defections could sink the bill. Top Senate Democrat Chuck Schumer blasted the bill as a "sham" that pads the pockets of the wealthy and insurance companies "at the expense of American families" who will be forced to pay more out of pocket for medical care."Senate Democrats will work hard to see that it is defeated," he said in a statement.