The insurance industry's leading lobbying group and the Blue Cross Blue Shield Association of health plans on Wednesday said they oppose the last-ditch Republican plan to repeal and replace Obamacare.

Both America's Health Insurance Plans and BCBSA said the Graham-Cassidy bill could further destabilize the individual insurance market.

The groups warned that the bill could reduce health coverage for many Americans and undermine Obamacare protections for people with pre-existing medical conditions.

Graham-Cassidy "would have real consequences on consumers and patients," AHIP President Marilyn Tavenner wrote in a letter to Senate leaders.

In its own statement, the Blue Cross Blue Shield Association said, "Although we support providing states with greater flexibility in shaping health care options for their residents, we share the significant concerns of many health care organizations about the proposed Graham-Cassidy bill.

A slew of patient and health provider groups oppose Graham-Cassidy, as does the AARP, the powerful lobbying group for older Americans.

In a report issued Wednesday, AARP said the bill "could increase premiums and out-of-pocket costs by as much as $16,174 a year for a 60-year-old earning $25,000 annually if they wanted to keep their current coverage."

A group of 10 bipartisan governors announced their opposition to the bill on Tuesday.

Senate Majority Leader Mitch McConnell, R-Ky., plans to hold a vote on the bill next week. But it is not clear if Republicans will have enough votes from their own members to pass the legislation.

Republican congressional leaders face a Sept. 30 deadline to pass the bill under the rules of reconciliation that are being used to fast-track the legislation.

The bill is being supported by the Trump administration. No Democrat or independent in Congress is expected to vote for the bill.

Graham-Cassidy would significantly cut federal health spending overall and eliminate Obamacare's expansion of Medicaid benefits to more poor adults, as well as federal subsidies to help middle- and low-income people buy private insurance.

In their place, Graham-Cassidy would block-grant federal funds to individual states to create their own health coverage systems.