US President-elect Donald Trump has described America's leading Democrat as a "clown" who behaves like a typical politician, but urged him to work with Republicans.
In early morning tweets, the incoming president attacked Senate minority leader Chuck Schumer - whom he has previously praised - amid a mounting row over health care reform.
Republicans have vowed to press ahead with the potentially unpopular campaign promise of gutting President Barack Obama's signature legislation.
The Affordable Care Act allowed millions of poorer Americans to get treatment, but was criticised for raising insurance premiums.
But Republicans, who control both houses of Congress and will take over the White House from 20 January, appear uncertain about what, if anything, should replace Obamacare.
With the party taking a political hit for appearing adrift in the opening days of the new Congress, Mr Trump pinned responsibility back on Democrats.
"The Democrats, lead by head clown Chuck Schumer, know how bad Obamacare is and what a mess they are in," Mr Trump said in a tweet.
"Instead of working to fix it, they do the typical political thing and BLAME. The fact is Obamacare was a lie from the beginning. 'Keep you doctor, keep your plan!' It is time for Republicans & Democrats to get together and come up with a healthcare plan that really works -- much less expensive & FAR BETTER!"
Republicans in Congress made their first moves to repeal the health care law yesterday, agreeing to begin the process of starving the system of funding.
Mr Obama has launched a parting offensive to try to save his reform.
He made a rare visit to Congress yesterday to rally Democrats for what is shaping up as the first major fight of the next administration.
Democratic Senator Tim Kaine, who ran for vice president on Hillary Clinton's losing ticket last year, said the president had advised Democrats not to work with Republicans unless they provide a plan to replace Obamacare.
"They will have shown us by the repeal that they are uninterested in our input and they will have also shown a heartlessness about 30 million people are going to lose insurance," he told CNN today.
However, he held the door open for cooperation, saying: "We will look at any suggestion that doesn't reduce coverage or increase cost or diminish the quality of care."
