The Republican plan to replace Obamacare has a healthproblem.

Related: Insurance top priority when choosingdoctor

On Wednesday, the U.S.’s biggest advocacy group for doctors cameout against House Republicans’ legislation, adding to growingopposition from the country’s top trade groups for physicians andhospitals who worry that it will leave more people uninsured orwith limited coverage.

In a letter to Congress, the American Medical Association saidWednesday it “cannot support the AHCA as it is currently written,”referring to the American Health Care Act, as the Republicanproposal to repeal and replace the Affordable Care Act isnamed.

The association calls itself the largest physician advocacygroup in the country, and backed the nomination of Tom Price asPresident Donald Trump’s Health and Human Services secretary andpoint person on the health law.

The association’s letter adds to growing objections to the bill,which would eliminate much of Obamacare and replace it with smallertax subsidies to buy insurance.

In the last several days, other major physician groups,including the American College of Physicians, the American Academyof Family Physicians and the American Psychiatric Association,have said said they have serious issues with or outright oppose theplan. Together they represent hundreds of thousands of U.S. doctorsand health professionals.

Related: Hospitals, advocates raise alarms about ACArepeal

Other industry trade groups have stayed largely neutral,including drugmakers and biotechnology companies. The healthinsurance lobby, America’s Health Insurance Plans, has yet to takea position on either side, though the group’s Chief ExecutiveOfficer Marilyn Tavenner said that “it’s important to us to keep asmany members covered as possible.” She spoke at the group’s annualpolicy conference in Washington on Wednesday.

Hospital opposition

The biggest hospital groups, the American Hospital Association and theFederation of American Hospitals, have also said they have seriousconcerns with the proposal

“We cannot support The American Health Care Act in its currentform,” the American Hospital Association, which represents about5,000 U.S. hospitals, said in a March 7 letter to Congress. TheFederation of American Hospitals, which represents for-profitchains including HCA Holdings Inc. and Community Health SystemsInc., also said it had “significant issues” with the plan.

“We want to make sure that whatever comes out of this changereally supports particularly those low-income Americans, whofrankly don’t have the resources to afford coverage,” Chip Kahn,CEO of the hospital federation, said Wednesday at the healthinsurance forum in Washington.

The legislation is going to be considered by two Housecommittees today as Republican leaders attempt to quickly get it tothe floor for a vote. Congressional actuaries have yet to issue a“score” that will show how much it will cost or save taxpayers, andhow many people will lose or gain insurance.

Coverage changes

Obamacare provided insurance to about 20 million people,bringing the U.S. uninsured rate to a record low. Under theRepublican plan, about 2 million to 4 million people would losecoverage in the individual market starting in 2020, while another 4million to 6 million would lose their Medicaid coverage, accordingto an estimate from S&P Global Ratings Tuesday.

The GOP plan has run into problems outside the health sector, aswell. Conservatives have said they may not support it in Congress,which could imperil its passage in the House, or in the Senate,where Republicans have only a razor-thin majority. It’s also beenpanned by health experts who say it will reduce insurance coverageand provide weak coverage.

Trump ran on a promise to repeal the 2010 health law known asObamacare, which he has said reduces employment and hasn’t workedto better health care, citing rising premiums and markets thathealth insurers have pulled back from.

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