This story was updated at 6:02 p.m. on Friday, Jan. 17, 2019, with more information.

NASHVILLE — A key architect of Gov. Bill Lee's ambitious but controversial Medicaid block-grant proposal for the TennCare Medicaid program is leaving state government.

Division of TennCare Director Gabe Roberts announced Friday he is departing the post March 22 to return to an unspecified job in the private sector.

The announcement comes as Trump administration officials continue to review Tennessee's precedent-shattering effort to transform much of the federal funding for the TennCare Medicaid health insurance program that covers some 1.4 million low-income Tennesseans.

Roberts, a TennCare veteran who became director earlier this year, said in a statement it has "been the honor of my professional life to serve the state of Tennessee during my seven years at TennCare and for serving alongside Governor Lee this past year."

After thanking his wife, Roberts also said he is "indebted to my incredible team who has worked tirelessly with stakeholders across the state for so long to ensure that our Medicaid program remains on the leading edge of positive transformation, innovation, and fiscal sustainability.

"I am excited to see what they will accomplish with Governor Lee on behalf of the state in the coming years," he said.

Lee said "we're grateful to Gabe Roberts for his many years of service to the state of Tennessee" and described Roberts as "instrumental in guiding TennCare during the first year of my administration, and I'm thankful for his leadership.

"While his service in state government is coming to an end for now, I'm certain our state will continue to benefit from his contributions in his future endeavors," Lee added.

TennCare spokeswoman Sarah Tanksley rejected any notion that Roberts' departure leaves the Lee administration in the lurch as officials try to work through the waiver with the federal Centers for Medicare and Medicaid Services and, if approved, implement it.

"No, it doesn't at all," Tanksley said in an email to the Times Free Press. "There are members of the executive team who were involved in the drafting of Amendment 42 who will be just as involved in discussions with CMS when those occur."

No replacement has been named.

Tennessee in November became the first state in the country to apply for a federal Medicaid waiver from the Trump administration, which has encouraged states to pursue them with an eye toward cutting federal health spending costs.

The waiver seeks to do away with many federal restrictions on how the state operates the program. It provides health coverage for low-income pregnant women, mothers and children as well as some elderly and disabled Tennesseans.

Critics, including congressional Democrats and health law experts, charge President Donald Trump has no authority to grant the waivers. They say it would require action by Congress, which is unlikely given Democrats' control of the U.S. House.

Tennessee's plan calls for converting some $7.9 billion in federal funding out of TennCare's total $12.1 billion budget to pursue innovations and, officials say, improve and expand services to existing enrollees. And Lee has held out the possibility of adding new low-income Tennesseans to the program.

Unlike a traditional block grant, the state's plan calls for annual inflation adjustments as well as provisions to allow more people to come onto the program. It also includes a novel cost-sharing provision tied to savings the state says its managed care program has already saved the federal government.

Still, fearful advocacy groups ranging from the American Cancer Society to the Tennessee Justice Center have attacked the plan.

During the state's waiver comment period, only a handful of companies, organizations or people out of nearly 1,800 voiced support for the waiver. If approved by the Centers for Medicare and Medicaid Services, it would have to come back to the Tennessee Legislature for approval before it could be implemented.

Contact Andy Sher at asher or 615-255-0550. Follow him on Twitter @AndySher1.