America's Health Insurance Plans, the lobbying group representing insurers, said Wednesday it opposes a Republican bill to overhaul Obamacare, in part because the bill could pave the way for states to implement their own single-payer healthcare systems.

The overhaul bill "would have real consequences on consumers and patients by further destabilizing the individual market; cutting Medicaid; pulling back on protections for pre-existing conditions; not ending taxes on health insurance premiums and benefits; and potentially allowing government-controlled, single-payer healthcare to grow," wrote Marilyn Tavenner, president and CEO of AHIP, in a letter to Senate leaders.

Sen. John Kennedy, R-La., has asked Republicans to add an amendment to the bill that would prohibit states from implementing a state-run health insurance system, but GOP Sen. Lindsey Graham of South Carolina, one of the bill's authors, has said states could try to implement such a system if they wanted.

California and Vermont tried to implement single-payer proposals under Obamacare but failed, largely because of cost. A single-payer proposal would remove customers from private coverage, a move that insurers oppose.

"To best serve every American, we need both a strong private market and an effective role for and partnerships with government," Tavenner wrote. "Building on the choice, competition and innovation of the private sector and the strength, security and dependability of public programs is a far more effective solution than allowing states to eliminate private insurance."

AHIP joins the association of 36 independent Blue Cross Blue Shield insurers in opposing the bill, along with the American Medical Association, the American Hospital Association and a group of 10 bipartisan governors. Outside conservative groups have given a tepid nod to the bill and 15 GOP governors support it.

The bill, introduced by GOP Sens. Lindsey Graham of South Carolina, Bill Cassidy of Louisiana, Dean Heller of Nevada and Ron Johnson of Wisconsin, would shift Obamacare's revenues to states in the form of block grants so they could implement their own healthcare systems. It also would repeal the individual and employer mandate.

Tavenner noted in her letter that the bill did not repeal the health insurance tax or the "Cadillac tax," both of which it has long lobbied against.

The letter said the organization's priorities were to stabilize the Obamacare exchanges, improve Medicaid, and cover people with pre-existing illnesses, goals that AHIP said the GOP healthcare bill did not address. The group said that the bill did not allow states enough time to plan their healthcare systems.

When asked Monday about the healthcare bill, AHIP told the Washington Examiner that it had not taken a position on the legislation.

Senate Majority Leader Mitch McConnell said Wednesday that he intended to bring the bill to the floor next week. The Senate faces a Sept. 30 deadline to pass the bill through a simple majority vote, known as reconciliation, according to a recommendation by the Senate parliamentarian.