With the U.S. facing massive overcrowding in its prisons, Attorney General Eric Holder called Monday for major changes to the nation’s criminal justice system that would scale back the use of harsh sentences for certain drug-related crimes.

In remarks to the American Bar Association in San Francisco, Holder said he also favors diverting people convicted of low-level offenses to drug treatment and community service programs, and expanding a prison program to allow for release of some elderly, nonviolent offenders.

“We need to ensure that incarceration is used to punish, deter and rehabilitate — not merely to convict, warehouse and forget,” Holder said.

In one important change, the attorney general said he’s altering Justice Department policy so that low-level, nonviolent drug offenders with no ties to large-scale organizations, gangs or cartels won’t be charged with offenses that impose mandatory minimum sentences.

Mandatory minimum prison sentences, a product of the government’s war on drugs that began in the 1980s, limit the discretion of judges to impose shorter prison sentences.

Under the changed policy, the attorney general said defendants will be charged with offenses for which accompanying sentences “are better suited to their individual conduct, rather than excessive prison terms more appropriate for violent criminals or drug kingpins.”

Holder’s comments drew bipartisan support on Capitol Hill.

Sen. Rand Paul, R-Ky., said he is encouraged by the Obama administration’s view that mandatory minimum sentences for nonviolent offenders promote injustice and do not serve public safety. Paul and Senate Judiciary Committee chairman Patrick Leahy, D-Vt., introduced legislation in March to grant federal judges greater flexibility in sentencing all crimes where a mandatory minimum punishment is considered unnecessary. Leahy commended Holder for his efforts on the issue and said his committee will hold a hearing on the bill next month.

Sen. Dick Durbin, D-Ill., the No. 2 Democrat in the Senate, said he looks forward to working on the issue with Holder and senators on both sides of the aisle who support change.

The impact of Holder’s initiative on mandatory minimum sentences could be significant, says Marc Mauer, executive director of the Sentencing Project, a nonprofit group involved in research and policy reform of the criminal justice system.

There are about 25,000 drug convictions in federal court each year, and 45 percent of those are for lower-level offenses such as street level dealers and couriers and people who deliver drugs, Mauer said.

The unanswered question is how each of the 94 U.S. attorneys offices around the country will implement changes, given the authority of prosecutors to exercise discretion in how they handle their criminal cases.

African-Americans and Hispanics likely would benefit the most from a change. African-Americans account for about 30 percent of federal drug convictions each year and Hispanics account for 40 percent, according to Mauer.

If state policymakers were to adopt similar policies, the impact of changes at the state level could be even broader, Mauer said. Currently, about 225,000 state prisoners are incarcerated for drug offenses, according to the U.S. Bureau of Justice Statistics.

Holder said mandatory minimum sentences “breed disrespect for the system. When applied indiscriminately, they do not serve public safety. They have had a disabling effect on communities. And they are ultimately counterproductive.”

Holder said new approaches — which he is calling the “Smart On Crime” initiative — are the result of a Justice Department review he launched early this year.

The attorney general said 17 states have directed money away from prison construction and toward programs and services such as treatment and supervision that are designed to reduce the problem of repeat offenders.

He cited investments in drug treatment in Texas for nonviolent offenders and changes to parole policies that he said brought about a reduction in the prison population of more than 5,000 inmates last year. He also pointed to Georgia, North Carolina, Ohio, Pennsylvania and Hawaii as states that have improved public safety while preserving limited resources.

Holder also said the department is expanding a policy for considering compassionate release for inmates facing extraordinary or compelling circumstances, and who pose no threat to the public. He said the expansion will include elderly inmates who did not commit violent crimes and who have served significant portions of their sentences.