A collection of 16 patient and healthcare provider groups is opposing the last shot Republicans have at tackling Obamacare.

The groups, which include the American Heart Association and American Cancer Society Cancer Action Network, say a bill to give Obamacare funding to states as block grants would roll back patients' access to good health coverage.

Republican Sens. Lindsey Graham of South Carolina, Bill Cassidy of Louisiana, Dean Heller of Nevada, and Ron Johnson of Wisconsin are co-sponsoring the legislation. The senators have deemed it to be the last shot at repealing Obamacare before a Sept. 30 deadline to get the bill approved in the Senate with only 51 votes.

However, the bill is running into severe pushback from patient groups, who said it would "limit funding for the Medicaid program, roll back important essential health benefit protections and potentially open the door to annual and lifetime caps on coverage, endangering access to critical care for millions of Americans."

The group charges that much of the proposal repackages the Better Care Reconciliation Act, which the Senate voted down in late July. The Senate also voted down a "skinny" repeal bill.

The four senators are hoping for a better outcome this time around.

The groups said that Congress instead needs to focus on an emerging bipartisan Obamacare stabilization package and reauthorizing the Children's Health Insurance Program that expires at the end of the month.

Among the 16 groups that signed the statement were the ALS Association, American Lung Association, American Diabetes Association, March of Dimes, and National Organization for Rare Diseases.