Story highlights Attorney General Eric Holder says plan could reduce federal prison population by thousands

Holder says penalties would still be tough for violent criminals

Making a rare appearance Thursday before the U.S. Sentencing Commission , Holder plans to endorse the commission's proposed change.

According to prepared remarks provided by the Justice Department, the change would "make the federal criminal justice system both more effective and more efficient when battling crime and the conditions and behaviors that breed it."

Holder says penalties would still be tough for violent criminals while finding ways to reduce the costs of the federal prison system.

The move, which the sentencing commission might vote on in April, aligns with Holder's "Smart on Crime" initiative.

Joining with conservative lawmakers and governors, Holder has pushed for reduced reliance on prison for certain nonviolent drug offenders.

The federal prison system holds 216,000 prisoners. With only 5% of the world's population, Holder notes, the Unites States has nearly 25% of the world's prisoners.

"This overreliance on incarceration is not just financially unsustainable -- it comes with human and moral costs that are impossible to calculate," Holder says in prepared remarks.