A Republican proposal to revamp the nation’s health care system would fundamentally alter Medicaid, threatening access to community-based services for people with developmental disabilities, advocates say.

The plan to repeal and replace the Affordable Care Act unveiled by leaders of the U.S. House of Representatives earlier this week calls for new limits on federal Medicaid spending.

Rather than provide matching grants to states to cover anyone who meets eligibility requirements, the federal government would impose what’s known as a per capita cap, providing a fixed amount of money for each beneficiary based on spending in 2016.

That would mark a dramatic shift for the state-federal program that has operated as an entitlement since its inception in 1965. And, such a change would trigger deep consequences for people with disabilities who rely on Medicaid to access everything from doctors to support services to live in the community, advocates say.

“The legislation revealed by House Republicans … is a giant step backwards in the treatment and care of individuals with disabilities,” said Curt Decker, executive director of the National Disability Rights Network. “It caps Medicaid funding which means a sharp reduction in services and availability of this important health care lifeline for children and adults with disabilities. In short, this plan is terrible.”

It’s not yet clear exactly how much money Uncle Sam would provide states for Medicaid under the new plan. However, an estimate from the nonpartisan Center on Budget and Policy Priorities suggests that a per capita cap would mean $116 billion less in federal funding for Medicaid over 10 years, with states left to make up the difference.

“Let there be no doubt about it — caps mean cuts,” said Nicole Jorwic, director of rights policy at The Arc. “This will lead to cuts in services and longer waiting lists.”

“Every service will be at stake if this bill passes,” Jorwic added. “States will have to make decisions about access and what services are provided based on their bottom lines, not what they need to do to meet the needs of their residents.”

People with developmental disabilities could lose home and community-based services and coverage of mental health, personal care, rehabilitative services, prescription drugs, respite care and other benefits could be slashed.

What’s more, the proposed legislation also calls for an end to Medicaid expansion, which advocates say has helped people with disabilities, their families and direct support providers access health care.

Disability advocacy groups are rallying their troops to oppose the measure by encouraging families to talk to their state and federal lawmakers about how Medicaid affects people with developmental disabilities on a personal level. Nearly 1,000 people from across the country participated in an emergency call this week to discuss next steps.

Meanwhile, House Republicans are planning to move quickly with the legislation and already held two committee hearings on Wednesday.

“With (this) legislation, we return power back to the states — strengthening Medicaid and prioritizing our nation’s most vulnerable,” said Rep. Greg Walden, R-Ore., who chairs the House Energy and Commerce Committee, in a statement.

However, there are signs that the health care overhaul may not be a done deal with Democrats and some Republicans expressing reservations about the proposal.

“It is very important for advocates to speak up and tell their stories,” Jorwic said.