WASHINGTON (Reuters) - U.S. President-elect Donald Trump on Tuesday pressured fellow Republicans working to repeal Obamacare in Congress to pass a replacement for the healthcare law at the same time or soon after they vote to dismantle it.

U.S. President-elect Donald Trump listens to questions from reporters while appearing with Alibaba Executive Chairman Jack Ma after their meeting at Trump Tower in New York, U.S., January 9, 2017. REUTERS/Mike Segar

Trump told the New York Times he wanted a substitute for President Barack Obama's 2010 healthcare law done "very quickly or simultaneously" to the vote to get rid of it. (nyti.ms/2ia9qLk)

The law, popularly known as Obamacare, has enabled millions of previously uninsured Americans to obtain health insurance, but Republicans condemn it as a government overreach.

With Trump set to succeed Obama on Jan. 20, Republicans, who control both chambers of Congress, face a dilemma. They have a chance to make good on their promise to gut the law, but forging an agreement on a replacement plan has eluded them.

If Congress does not put in place a substitute, millions of Americans with the insurance may be at risk of losing coverage.

The law extended insurance coverage to uninsured Americans by expanding the Medicaid program for the poor and creating online exchanges where people can shop for health insurance plans. It also provides subsidies to help individuals and families afford those plans.

House of Representatives Speaker Paul Ryan said on Tuesday that some elements of an insurance substitute likely would be ready when lawmakers vote to repeal Obamacare, but others would take longer.

Some Republicans have said it could take up to two years to craft a replacement. Trump said a delay of that length was unacceptable, telling the Times: “It won’t be repeal and then two years later go in with another plan.”

Senate Republican Leader Mitch McConnell said Trump’s comments were “not inconsistent” with lawmakers’ plans.

The Senate is set to vote this week on a timeline to draft legislation repealing Obamacare. If it passes, the House would vote next. But a vote to actually repeal the law would come later.

Senate Democratic Leader Chuck Schumer said Republicans were mired in “internecine fights” and called on Trump to publish his own Obamacare substitute.

Trump during the 2016 election campaign put forth general principles for health reform, such as removing the mandate that all Americans have insurance or pay a tax and expanding the use of tax-free health savings accounts, but he did not release a full plan.

“If they are repealing, they have an obligation to show us a full replacement plan, not just a little piece of it,” Schumer said. “And once they show us that plan, we’ll give them our opinion of it.”

U.S. Senator Lamar Alexander, a Republican who heads the health committee, said some Obamacare replacement steps need to be in place before March 1, when insurance companies will be deciding whether to offer plans for 2018.

In a speech on Tuesday, Alexander said interim steps could include letting people use Obamacare subsidies to purchase other plans or giving states flexibility to determine which benefits insurance plans must cover.

House Speaker Ryan said Republicans would like to pack whatever replacement provisions they can into repeal legislation. Because the Senate plans to use a budget procedure known as reconciliation, they only need majority support in the 100-member Senate where Republicans hold 52 seats.

Republican Senator Orrin Hatch, who heads the finance panel, said Senate rules for the reconciliation process could make it difficult to put replacement provisions in the repeal bill.

“If he can come up with something that would help push this forward, I’d be all for it,” Hatch said of Ryan.