(CNN) -- Attorney General Jeff Sessions officially came out against a renewed effort for criminal justice reform Wednesday as lawmakers on Capitol Hill prepare for a mark-up of a bipartisan bill.
In a letter obtained by CNN, Sessions told Sen. Chuck Grassley of Iowa, the top Republican on the Senate Judiciary Committee, that the Sentencing Reform and Corrections Act of 2017 "would reduce sentences for a highly dangerous cohort of criminals, including repeat dangerous drug traffickers and those who use firearms, and would apply retroactively to many dangerous felons, regardless of citizenship or immigration status."
"In my opinion, if passed in its current form, this legislation would be a grave error," Sessions added.
Grassley, who has been leading a bipartisan group of senators sponsoring the bill, promptly shot back on Twitter once the letter became public Wednesday, saying, "AGs execute laws CONGRESS WRITES THEM!"
A major overhaul of the criminal justice system stalled during the end of the Obama administration, as lawmakers have remained divided over reducing mandatory minimum sentences, but some senators, including Kamala Harris, D-California, and Rand Paul, R-Kentucky, have tried to move forward with more incremental changes, such as encouraging states to end their cash bail systems.
Last month, Sessions attended a meeting at the White House on prison reform, and he suggested in Wednesday's letter that he continues to support those efforts.
"[A]s you know, the Administration supports helping former inmates who have served lawfully imposed sentences and have demonstrated a commitment to a better life, and is working closely with Congress to achieve a responsible reform along those lines," Sessions wrote.
After the White House meeting, Mark Holden, the senior vice president and general counsel of Koch Industries, told CNN that Sessions "is totally on board" with prison reform, but Holden suggested that broader criminal justice reform efforts might need to be done gradually to satisfy Sessions and other holdouts.
Several senators appeared ready to move forward with prison reform as a first step during a Senate Judiciary Committee meeting last week.
"I'm worried that if we just revisit the Sentencing Reform and Corrections Act, which failed during the Obama administration, given this change in the new administration and their views on the sentencing reform component of it, that we're going to end up with nothing to show for our efforts," said Republican Sen. John Cornyn of Texas."I think there is a path forward starting with the prison reform piece."
CNN's Eli Watkins contributed to this report.
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