Alaska Gov. Bill Walker Mark Thiessen/AP A bipartisan group of 10 governors on Tuesday attacked the latest Republican attempt to repeal and replace the Affordable Care Act in a strongly worded letter to Senate leaders.

The letter to Senate Majority Leader Mitch McConnell and Senate Minority Leader Chuck Schumer said the Graham-Cassidy-Heller-Johnson healthcare legislation should not be considered. Instead, the group said, the Senate should prioritize the bipartisan bill being drafted in the Senate Health, Education, Labor and Pensions Committee to stabilize the law known as Obamacare.

"As you continue to consider changes to the American health care system, we ask you not to consider the Graham-Cassidy-Heller-Johnson amendment and renew support for bipartisan efforts to make health care more available and affordable for all Americans," the letter said. "Only open, bipartisan approaches can achieve true, lasting reforms."

The authors of the Senate legislation have consistently cited the ability for states to determine their own healthcare expenditures by proposing to provide states federal funding in a block grants. Critics of the bill say that while it gives states the money up front, it also slices the amount of money most states receive.

Nine of the 10 governors who signed the letter represent states that expanded the federal Medicaid program under Obamacare. That expansion would no longer receive funding under the GCHJ bill.

The group of governors includes Republicans John Kasich of Ohio and Brian Sandoval of Nevada along with Democrats John Hickenlooper of Colorado and John Bel Edwards of Louisiana (the home state of Sen. Bill Cassidy, an author of the bill).

Alaska Gov. Bill Walker, who had not joined the group in opposing previous versions of GOP healthcare legislation, also signed onto the letter. Alaska Sen. Lisa Murkowski voted against the original Senate healthcare plans in July and is seen as a pivotal vote on the GCHJ.

Kasich and Hickenlooper led a similar group when they debuted a stabilization plan for the Obamacare markets, which bears striking similarities to the discussions in the HELP Committee. The governors praised that work. From the letter:

"Chairman Lamar Alexander and Ranking Member Patty Murray have held bipartisan hearings in the Senate’s Health, Education, Labor and Pensions (HELP) Committee, and have negotiated in good faith to stabilize the individual market. At the committee’s recent hearing with Governors, there was broad bipartisan agreement about many of the initial steps that need to be taken to make individual health insurance more stable and affordable. We are hopeful that the HELP committee, through an open process, can develop bipartisan legislation and we believe their efforts deserve support."

Republicans have until September 30 to pass the GCHJ with a simple majority.