Sen. Thom Tillis (R-N.C.) said Sunday that the Senate version of President Trump’s massive spending bill “will betray the very promise” the president made when he pledged not to interfere with people’s Medicaid benefits.

Tillis — who voted against the bill in a key procedural vote Saturday night and announced Sunday he would not run for reelection — delivered a scathing rebuke of the president’s agenda-setting bill in a Senate floor speech, explaining his position and pledging to withhold his vote unless his concerns about drastic cuts to Medicaid are addressed.

“What do I tell 663,000 people in two years or three years, when President Trump breaks his promise by pushing them off of Medicaid because the funding’s not there anymore, guys? I think the people in the White House… advising the president are not telling him that the effect of this bill is to break a promise,” Tillis said in his floor speech.

Tillis said he gathered various estimates about the effect of the provider-tax provision and presented them to White House experts, who “admitted that we were right” but said North Carolina is just “going to have to make it work.”

Tillis appealed to the president directly, telling him that his advisers are not informing him of the actual consequences for Medicaid coverage that will inevitably transpire if the bill passes in its current form.

“Now Republicans are about to make a mistake on health care and betraying a promise,” Tillis said. “It is inescapable that this bill in its current form will betray the very promise that Donald J. Trump made in the Oval Office or in the cabinet room, when I was there with finance, where he said, we can go after waste, fraud, and abuse on any programs.”

“Now, those amateurs that are advising him — not Dr. Oz, I’m talking about White House health care experts — refuse to tell him that those instructions, that were to eliminate waste, fraud and abuse, all of a sudden eliminates a government program that’s called the provider tax,” he continued.

Tillis criticized the Senate GOP for rushing to meet Trump’s July 4 deadline, rather than taking the time to consider the impact on their states. He also said he would be inclined to support the House version of the Medicaid proposal and lamented his party’s resistance to considering changes.

“I am telling the president that you have been misinformed,” Tillis said. “You supporting the Senate mark will hurt people who are eligible and qualified for Medicaid.”

“I love the work requirement. I love the other reforms in this bill. They are necessary, and I appreciate the leadership of the House for putting it in there,” he continued.

“In fact, I like the work of the House so much that I wouldn’t be having to do this speech if we simply started with the House mark. I’ve talked with my colleagues in North Carolina. I know that we can do that. And I believe that we can make sure that we do not break the promise of Donald J. Trump, that he’s made to the people who are on Medicaid today.”

He closed out his speech pledging doubling down on his position against the bill.

“We owe it to the American people, and I owe it to the people of North Carolina, to withhold my affirmative vote until it’s demonstrated to me that we’ve done our homework, we’re going to make sure that we fulfill the promise. And then I can feel good about a bill that I’m willing to vote for,” he said. “But until that time, I will be withholding my vote.”

Trump had attacked Tillis for his opposition to the bill and, this weekend, floated the prospect of backing a primary challenge to the senator.