Obama, Team Trump in health care showdown

 US President Barack Obama attends the Armed Forces Full Honor Review Farewell Ceremony for Obama at Joint Base Myers-Henderson Hall in Arlington, Virginia, January 4, 2017.

US President Barack Obama called on congressional Democrats Wednesday to "fight" to preserve his signature health care reform, with its future in doubt as Donald Trump's incoming administration vowed a swift repeal of the controversial law.

Obamacare, the fruit of an eight-year drive to extend medical coverage to tens of millions of Americans, will come under sustained assault when Trump takes office on January 20 with Republican majorities in both chambers of Congress.

But the debate over US health care began in earnest Wednesday at the highest levels, with Obama and Vice President-elect Mike Pence making duelling visits to Capitol Hill to urge their legislative foot soldiers to gird for battle.

"I envy you for the opportunity you are going to have to engage in this fight to protect health care for the American people," the outgoing president told Senate and House Democrats, according to Senator Ed Markey, who attended the 100-minute meeting.

After a crushing election loss, Democrats may have limited options for stalling a repeal of Obamacare without significant Republican defections.

They also face criticism that Obama's reforms have led to rising insurance premiums and a string of technical problems.

But certain elements of Obamacare remain popular, notably the provisions barring companies from refusing coverage due to pre-existing conditions and allowing children to retain coverage on family plans through age 26.