Sen. Chuck Grassley, R-Iowa, and Attorney General Jeff Sessions are close friends, but you wouldn’t know that based on the fiery exchange between them this week over the hot-button issue of sentencing reform.

The AG touched off the dispute by sending a letter telling the Judiciary Committee chairman it would be a “grave error” for his prison sentencing reform legislation to pass into law.

“I’m just very incensed that he would send that letter,” Grassley told reporters Thursday.

Suggesting he felt some hint of betrayal, Grassley recalled their personal history.

“All I’ve done to help him in his job, number one, getting the job, number two, helping with all these assistant attorney generals … a lot of them have been very controversial,” Grassley said. “When the president wanted to fire him, I said the president shouldn’t do that.”

Grassley’s bill would reduce mandatory minimum prison sentences by instead targeting the worst drug offenders and criminals.

But Sessions, who has effectively declared a new war on drugs, took aim at the legislation and warned of “potentially dire consequences” if the bill becomes law.

“Passing this legislation to further reduce sentences for drug traffickers in the midst of the worst drug crisis in our nation’s history would make it more difficult to achieve our goals,” Sessions wrote. “The bill weakens penalties for repeat, serious drug traffickers, including those who used a gun and those with significant criminal histories, and reduces the sentences of and potentially allows for the early release of many dangerous felons in prison now.”

This prompted an angry tweet on Wednesday from Grassley, who wrote:

“Incensed by Sessions letter An attempt to undermine Grassley/Durbin/Lee BIPARTISAN criminal justice reforms This bill deserves thoughtful consideration b4 my cmte. AGs execute laws CONGRESS WRITES THEM!”

Grassley maintains that the bill has “the right balance of improving public safety and ensuring fairness in the criminal justice system.”

The split underscores how the issue of sentencing reform has divided conservatives. A similar bill backed by Grassley two years ago never reached the Senate floor due to conservative opponents, like former Alabama senator Sessions, and a tough election map for Republicans senators.

Grassley’s objections this week also centered on Sessions getting involved in his committee’s markup of the bill.

“He is now the attorney general and is charged with executing the laws that Congress passes, not interfering with the legislative process,” Grassley stated in prepared remarks before the committee. “Certainly we value input from the Department of Justice, but if ... Sessions wanted to be involved in marking up this legislation, maybe he should have quit his job and run for the Republican Senate seat in Alabama.”

Sessions vacated his Senate seat last year to become President Trump’s attorney general.

Grassley said he talked to Sessions many times about the bill and they both believe in being tough on crime.

The bipartisan bill with 22 co-sponsors was eventually voted out of committee 16-5 on Thursday. It’s unclear if it will get a floor vote.