Just a week after submitting a letter to the federal government to reject Gov. Roy Cooper’s proposal to expand North Carolina’s Medicaid program, Republican leaders in the General Assembly announced late Friday they would file a federal lawsuit to block the move.

Senate Leader Phil Berger, R-Rockingham, and House Speaker Tim Moore, R-Cleveland, also questioned the governor’s nomination of a high-ranking Obama administration Medicaid official to become secretary of the state Department of Health and Human Services.

Read the court filing here.

In their joint statement, Berger and Moore attacked Cooper’s unilateral decision to enroll between 500,000 and 650,000 uninsured people in Medicaid, most of whom would be able-bodied, working-age males, instead of the traditional populations of children, single mothers, the aged, poor, and disabled. The expansion is estimated to cost about $6 billion over 10 years.

“Unlike others, this is the first time we will be plaintiffs in a lawsuit, and it is not a decision we’ve made lightly — but unfortunately our multiple attempts to amicably convince Gov. Cooper to follow the law have fallen on deaf ears,” Berger and Moore said in their release.

“Cooper’s brazen decision to press on with his unconstitutional Obamacare expansion scheme and ignore the General Assembly’s constitutional role to make laws requires swift legal action,” they said.

“Today has raised even more serious questions about how closely Gov. Cooper and the Obama administration have coordinated to force an unconstitutional Obamacare expansion in the last few days of the president’s administration, with the governor offering a cabinet post to a senior Obama administration official leading the very organization tasked with reviewing his proposal,” they said.

Mandy Cohen, chief operating officer at the federal Centers for Medicare and Medicaid Services, is Cooper’s nominee to become DHHS secretary. CMS must decide whether to approve Cooper’s expansion request, or grant Berger and Moore’s request to turn it down.

The legislative leaders said there is “a major conflict of interest” in the nomination because Cohen is “the same Obamacare proponent who is vetting the state’s application in the final days of the Obama administration.”

Announcement of the pending litigation comes a day after the release of a state audit that determined the state Medicaid program was rife with errors when determining eligibility for services.

State Rep. Nelson Dollar, R-Wake, and former DHHS secretary Lanier Cansler both have said approval by the lame-duck Obama administration of Cooper’s Medicaid expansion request would be unprecedented in its swiftness.

Dollar said Cooper’s action is illegal, and he is confident if the Obama administration approves it, President-elect Donald Trump would rescind the action.

Even if the plan were approved, and Trump reversed the decision, “state taxpayers could not recoup the millions of dollars in upfront implementation expenses the governor’s reckless action could cost them,” Berger and Moore said.

Berger and Moore, the release said, steadfastly maintain that Cooper does not have the authority to expand Obamacare unilaterally, his administration cannot take steps to increase Medicaid eligibility, and the state constitution does not allow him to spend billions of state tax dollars to expand Obamacare without legislative approval.

Cooper has said he could fund the state’s matching share of expansion costs by imposing a voluntary assessment on hospitals. The North Carolina Hospital Association has not supported that proposal.