The associations that played a role in the passage of 2010’s Affordable Care Act (ACA), also known as Obamacare, are not offering the same level of support to the Republican Party’s replacement plan.

The initial version of the American Health Care Act, released this week by House Republicans, has drawn criticism from some of the country’s largest healthcare associations. In a letter sent to leading members of two prominent House committees Tuesday, for example, the American Medical Association was quick to criticize the potential risks [PDF] the AHCA could create for the Americans already covered by the ACA.

“More than 20 million Americans currently have healthcare coverage due to the Affordable Care Act (ACA), and among the AMA’s highest priorities for ongoing health system reform efforts is to ensure that these individuals maintain that coverage,” wrote AMA CEO and Executive Vice President James L. Madara, M.D. “While we agree that there are problems with the ACA that must be addressed, we cannot support the AHCA as drafted because of the expected decline in health insurance coverage and the potential harm it would cause to vulnerable patient populations.”

AMA added that there were concerns with the shift toward age-based tax credits, along with the rollback of Medicaid expansions and measures that target Planned Parenthood, among other things.

“As drafted, the AHCA would result in millions of Americans losing coverage and benefits,” AMA President Andrew W. Gurman, M.D., said in a news release. “By replacing income-based premium subsidies with age-based tax credits, the AHCA will also make coverage more expensive—if not out of reach—for poor and sick Americans.”

AMA’s criticism makes it the third major association that has come out against the healthcare bill. Earlier this week, both the American Hospital Association (AHA) and AARP spoke out against the AHCA.

AARP, which represents millions of older Americans, specifically took issue with cuts to Medicare along with the potential of increased premiums.

“Older Americans need affordable healthcare services and prescriptions,” argued AARP Executive Vice President Nancy LeaMond. “This plan goes in the opposite direction, increasing insurance premiums for older Americans and not doing anything to lower drug costs.”

And AHA joined in on a letter to members of Congress with a number of other hospital groups, including America’s Essential Hospitals, the Association of American Medical Colleges, the Catholic Health Association of the United States, the Children’s Hospital Association, the Federation of American Hospitals, and the National Association of Psychiatric Health Systems.

“[M]aintaining deep provider reductions while dramatically reducing coverage will reduce our ability to provide essential care to those newly uninsured and those without adequate insurance,” the groups stated in the joint letter [PDF]. “As a result, we cannot support the American Health Care Act as currently written.”

While both the House Ways and Means and Energy and Commerce committees voted to advance the bill, it faces some significant tests in the coming days—specifically from the Congressional Budget Office, which has not yet publicly assessed or scored the AHCA.

House Majority Leader Kevin McCarthy, House Speaker Paul Ryan, and Rep. Greg Walden discuss the American Health Care Act. (Eric Thayer/Reuters)