Attorney General Jeff Sessions on Wednesday called Senate Judiciary Committee Chairman Chuck Grassley’s latest sentencing reform legislation a “grave error," saying it would lighten sentences for dangerous drug traffickers.

“In recent years, convicted drug traffickers and other violent criminals have received significant sentencing breaks from the federal courts and the United States Sentencing Commission,” Sessions wrote in a letter to Grassley. “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 and have potentially dire consequences.”

Sessions added that the legislation would reduce sentences for what he called a “highly dangerous cohort of criminals including repeat dangerous drug traffickers and those who use firearms.”

The legislation introduced by Grassley and Senate Minority Whip Dick Durbin, D-Ill., in October would reduce mandatory minimum sentences for nonviolent repeat drug offenders, and eliminate the three-strike mandatory life in prison provision that critics said dramatically increased the nation's prison population.

It would also give judges more discretion in how the sentence non-violent offenders.

The Senate Judiciary Committee, which included Session as a member when he was in the Senate, is poised to mark up the legislation Thursday.

Sessions opposed similar legislation when he was a senator on the committee in 2016.

Since becoming the nation’s top law enforcement officer roughly a year ago, Sessions has made fighting violent crime and drug offenses a top priority.

Last year, he issued a memo instructing all U.S. Attorneys' offices to charge offenders with the highest provable offense.

Grassley responded to Sessions in a tweet Wednesday afternoon.

“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!” he said.