Conservatives rebel against Republican healthcare reform

US President Donald Trump on Tuesday endorsed Republican legislation to replace the Obamacare healthcare law but the measure faced a rebellion by conservative groups and lawmakers, complicating its chances for passage in the US Congress.

Republican US House of Representatives leaders on Monday unveiled legislation to do away with Obamacare, eliminating the requirement that most Americans obtain medical insurance and creating a system of tax credits to coax people to purchase private insurance on the open market.

The 2010 Affordable Care Act, known as Obamacare and passed by Democrats over unified Republican opposition, is popular in many states, even some controlled by Republicans. It has brought medical coverage to about 20 million previously uninsured Americans.

Speaker Paul Ryan said he could guarantee that he had enough votes to win passage of the measure in the House, adding that conservatives should be excited about the plan to repeal and replace Democratic former President Barack Obama's signature domestic policy achievement.

House committees plan to begin voting on the legislation on Wednesday.

But conservatives slammed the proposal, with Republican Senator Mike Lee calling it "exactly the type of back-room dealing and rushed process that we criticised Democrats for."

Democrats and some moderate Republicans said the new House measure would hit lower-income Americans by rolling back the expansion of the Medicaid health insurance program for the poor.

Conservative opponents said the legislation maintains some Obamacare regulations and mandates that have caused rising insurance prices, creates a new entitlement in the form of tax credits and fails to embrace free-market ideals.

Democrats denounced the proposal as taking away health insurance from millions of Americans and benefiting the rich.

Trump said the plan was open to negotiation, but said it had already earned support "from everybody." Vice President Mike Pence described it as a "framework," signalling the measure was far from its final form. Health and Human Services Secretary Tom Price called it "a work in progress."

The proposal represented a key step toward carrying out pledges by Trump and congressional Republicans to dismantle Obamacare.