Attorney General Eric Holder on Thursday endorsed shorter prison sentences for most drug offenders, saying the U.S. was wasting money on overcrowded jails and that the stiffest penalties should be reserved for violent crimes.

"This overreliance on incarceration is not just financially unsustainable, it comes with human and moral costs that are impossible to calculate," Holder said in remarks to the U.S. Sentencing Commission.

“Certain types of cases result in too many Americans going to prison for far too long, and at times for no truly good public safety reason,” he added.

The Justice Department estimates that the plan would trim the federal prison population by 6,550 inmates over the next five years and reduce their sentences by an average of 11 months. In total, the new rules would affect roughly 70 percent of all drug cases brought by federal prosecutors.

The commission is expected to approve the framework in April.

The Obama administration has already called for reforms to what it sees as racial disparity in prison sentencing, as Holder previously directed prosecutors not to charge nonviolent drug offenders with crimes that carry mandatory minimum sentences.

And President Obama recently declared that marijuana, for example, was not that different from cigarettes and no more dangerous than alcohol. Last month, the attorney general also instructed banks they could conduct business with legal marijuana dispensers.

Holder noted Thursday that the U.S. makes up roughly 5 percent of the global population while accounting for a quarter of its prisoners.

There has been growing movement behind similar proposals among both Republicans and Democrats, creating the possibility of rare bipartisan consensus on a big-ticket item in Washington.

An Obama-backed sentencing bill on Capitol Hill has sponsors ranging from Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., to Sen. Mike Lee, R-Utah, a Tea Party favorite.

However, critics argue that the proposals could have damaging effects on public safety.