Despite the general view that health insurance companies would benefit from a free and open market, two of the biggest trade groups for insurers — Blue Cross Blue Shield Association and America’s Health Insurance Plans — announced their first opposition to the Republicans’ latest plan to repeal and replace Obamacare.

Both the Blue Cross and the AHIP came out against the so-called Graham-Cassidy bill Wednesday, arguing that the legislation would lead to an unstable market that would harm both insurers and patients.

“The bill contains provisions that would allow states to waive key consumer protections, as well as undermine safeguards for those with pre-existing medical conditions,’’ the Blue Cross association said in a statement. “The legislation reduces funding for many states significantly and would increase uncertainty in the marketplace, making coverage more expensive and jeopardizing Americans’ choice of health plans.”

The AHIP doubled down on those sentiments, writing that the bill “would have real consequences on consumers and patients by further destabilizing the individual market” and could “potentially allowing government-controlled, single payer health care to grow,” in a letter to Senate majority and minority leaders Mitch McConnell (R-Ky.) and Chuck Schumer (D-N.Y.).

The insurance trade associations’ resistance joins a number of health care groups already speaking out against the proposed bill, including the American Medical Association, the American Hospital Association and the American Association of Retired Persons.

The Graham-Cassidy bill, named after two of its drafters, Sens. Lindsey Graham (R-S.C.) and Bill Cassidy (R-La.), has a voting deadline of Sept. 30. The Senate is expected to vote on the legislation next week after several previously unsuccessful attempts earlier this year.

President Donald Trump talked up the bill Wednesday, saying that it has “a very good chance” of passing in the Senate.