President-elect Donald J. Trump demanded on Tuesday that Congress immediately repeal the Affordable Care Act and pass another health law quickly. His remarks put Republicans in the nearly impossible position of having only weeks to replace a health law that took nearly two years to pass.
“We have to get to business,” Mr. Trump told The New York Times in a telephone interview. “Obamacare has been a catastrophic event.”
Mr. Trump appeared to be unclear both about the timing of already scheduled votes in Congress and about the difficulty of his demand — a repeal vote “probably some time next week” and a replacement “very quickly or simultaneously, very shortly thereafter.”
But he was clear on one point: Plans by congressional Republicans to repeal the health law now, then take years to create and implement a replacement law are unacceptable to the incoming president.
Republican leaders have made the repeal of President Obama’s signature domestic achievement a top priority. They hope that the Senate will vote on Thursday and the House will vote on Friday to approve parliamentary language created to protect repeal legislation from a filibuster in the Senate.
The House speaker, Paul D. Ryan of Wisconsin, who consults often with Mr. Trump, set out a similar timetable on Tuesday, saying that a bill to repeal the health care law would include some legislation to replace aspects of it, though Republicans have yet to agree on the details of their alternative.
“It is our goal to bring it all together concurrently,” Mr. Ryan said.
But those ambitions will be difficult to achieve and will almost certainly require Democratic cooperation. Until now, Republicans could vote to repeal Mr. Obama’s health law with no fear that they would have to live with the political consequences of scuttling a law that provides health care for 20 million Americans and protects millions more from discrimination for pre-existing medical conditions, ends lifetime caps on insurance coverage and allows children to remain on their parents’ insurance policies until age 26.
With complete control of Washington, what comes next in health policy will belong to the Republican Party. For several days, congressional Republicans of diverse political views — moderates and conservatives alike — have been saying they are nervous about repealing the law without any clear path forward. Five Senate Republicans have pressed to delay the deadline for committees to produce repeal legislation until March, and several House Republicans are also demanding that the pace slow down.
“In an ideal situation, we would repeal and replace Obamacare simultaneously, but we need to make sure that we have at least a detailed framework that tells the American people what direction we’re headed,” said one of those five Republicans, Senator Susan Collins of Maine.
As it stands, the budget resolution that will fast-track that vote gives Senate and House committees until Jan. 27 to write legislation that would repeal major provisions of the health care law. But the schedule for action on that legislation, its effective date and the timetable for phasing in a new system of health insurance coverage are all unresolved questions.
Even the Jan. 27 deadline is not enforceable or particularly meaningful, Senate aides said, indicating that Congress could follow any timetable its leaders might prescribe.
That uncertainty apparently persuaded Mr. Trump to leap into the fray. Not only did he try to steel Republican spines, but he threatened Democrats who might stand in his way, saying he would campaign against them, especially in states that he won in November.
“It may not get approved the first time, and it may not get approved the second time, but the Democrats who will try not to approve it” will be at risk, he said, warning that “they have 10 people coming up” for re-election in 2018. That alluded to Democratic senators in states he won.
“I won some of those states by numbers that nobody has seen. I will be out there campaigning,” he said.
He described the health law as a catastrophe. “I feel that repeal and replace have to be together, for, very simply, I think that the Democrats should want to fix Obamacare,” he said. “They cannot live with it, and they have to go together.”
After meeting on Tuesday with House Republicans, Mr. Ryan took a similar tone, calling the campaign to repeal the health law “a rescue mission to save families who are getting caught up in the death spiral that has become Obamacare.”
Aides to Mr. Ryan said the effort to dismantle the Affordable Care Act would include not only the main bill that would be protected from a filibuster in the Senate, but also legislation that would not enjoy such protections. That legislation would take Democratic cooperation to be passed because Senate Republicans are eight votes short of a filibuster-proof majority.
Congressional Democrats say that the Affordable Care Act, far from being in a “death spiral,” is one of the best health laws since the creation of Medicare and Medicaid in 1965. And the Obama administration reported on Tuesday that more than 11.5 million people nationwide had signed up for health insurance or been automatically re-enrolled under the Affordable Care Act as of Dec. 24, 2016, an increase of nearly 300,000 from this time last year.
Of that total, officials said, more than 8.7 million people came in through HealthCare.gov, the online federal marketplace, and 2.8 million were enrolled in states using their own marketplace platforms.
“Today’s data show that this market is not merely stable, it is actually on track for growth,” Aviva Aron-Dine, a senior counselor to Sylvia Mathews Burwell, the secretary of health and human services, said in a conference call with reporters. “Today we can officially proclaim these death spiral claims dead.”
The fourth annual open enrollment period started on Nov. 1 and ends on Jan. 31, 11 days after Mr. Trump’s inauguration.
The enrollment numbers have some Republicans nervous. “The fear is that the strategy is repeal and delay, and then hope for the best, when we should be planning for the worst,” said Representative Charlie Dent of Pennsylvania, a chairman of the moderate Republican caucus known as the Tuesday Group.
Republican leaders tried on Tuesday to ease such concerns. But they may be making promises that will be difficult to keep.
“Let me be clear,” Representative Cathy McMorris Rodgers of Washington, the chairwoman of the House Republican Conference, told reporters. “No one who has coverage because of Obamacare today will lose that coverage. We’re providing relief. We aren’t going to pull the rug out from anyone.”
The Obama administration also provided new information to Congress on Tuesday about one of the most unpopular provisions of the health care law, which imposes tax penalties on people who go without insurance and do not qualify for an exemption from the requirement to have coverage.
The commissioner of the Internal Revenue Service, John A. Koskinen, reported that 6.5 million taxpayers were subject to penalties last year. The penalties totaled $3 billion, he said. The average payment was about $470.
Under another section of the health law, low- and moderate-income people can obtain subsidies, in the form of tax credits, to help pay for insurance bought through a public marketplace. In 2016, Mr. Koskinen said, 5.3 million taxpayers claimed $19.2 billion in premium tax credits, for an average of about $3,620.