President Barack Obama exhorted fellow Democrats on Wednesday to preserve his legacy-defining healthcare law as Republicans moved ahead with their long-sought bid to scrap it in what Vice President-elect Mike Pence called the "first order of business" of Donald Trump's administration.

The emerging Democratic strategy is to warn that Republicans risk throwing the entire US healthcare system into chaos by moving to dismantle the 2010 Affordable Care Act, popularly known as Obamacare, without a plan to replace it.

Republicans argue that the system is already broken and that they will help more people gain coverage by repealing the law while working to minimize disruptions to those who depend on it.

Both Obama and Pence visited Capitol Hill for closed-door discussions on Obamacare.

Pencemet Republican lawmakers to plot the path forward on scuttling the law.

"The first order of business is to keep our promise to repeal Obamacare and replace it with the kind of healthcare reform that will lower the cost of health insurance without growing the size of government," Pence told a news conference.

Down the hall from Pence, Obama, who hands over the presidency to Trump on Jan 20, urged Democratic lawmakers to protect his signature domestic policy. He told reporters his message was: "Look out for the American people."

-reuters