The American Hospital Association opposes a Republican effort to overhaul Obamacare that would fund healthcare in states through block grants.

"We believe that coverage could be at risk for tens of millions" under the bill, said Rick Pollack, president and CEO of the American Hospital Association. "We continue to urge senators to work in a bipartisan manner to address the challenges facing our healthcare system."

The overhaul effort has been touted by its supporters as a move to reignite GOP efforts on healthcare. It was introduced by Republican Sens. Lindsey Graham of South Carolina, Bill Cassidy of Louisiana, Dean Heller of Nevada and Ron Johnson of Wisconsin, and would repeal the individual and employer mandates while shifting revenue from Obamacare to states so they can craft their own plans.

The bill faces a Sept. 30 deadline to pass it through reconciliation, which allows a simple majority of senators to pass a bill instead of the 60 normally needed to break a filibuster. A group of bipartisan senators has been trying to reach a deal to stabilize the Obamacare exchanges but have not been able to come to an agreement yet.

The American Hospital Association encouraged those efforts by the Senate Health, Education, Labor and Pensions Committee.

The Graham-Cassidy bill "would erode key protections for patients and consumers and does nothing to stabilize the insurance market now or in the long term. In addition, the block grant to provide support for the expansion population expires in 2026, thereby eliminating coverage for millions of Americans. For these reasons, we oppose the Graham-Cassidy plan," the hospital group said Tuesday.