Attorney General Eric H. Holder Jr. announced Monday that low-level, nonviolent drug offenders with no ties to gangs or large-scale drug organizations will no longer be charged with offenses that impose severe mandatory sentences.

The new Justice Department policy is part of a comprehensive prison reform package that Holder unveiled in a speech to the American Bar Association in San Francisco. He also introduced a policy to reduce sentences for elderly, nonviolent inmates and find alternatives to prison for nonviolent criminals.

Justice Department lawyers have worked for months on the proposals, which Holder wants to make the cornerstone of the rest of his tenure.

“We must face the reality that, as it stands, our system is, in too many ways, broken,” Holder said. “And with an outsized, unnecessarily large prison population, we need to ensure that incarceration is used to punish, to deter and to rehabilitate — not merely to warehouse and to forget.”

“A vicious cycle of poverty, criminality and incarceration traps too many Americans and weakens too many communities,” Holder said Monday. (Excerpts of his ­prepared remarks were provided Sunday to The Washington Post.) He added that “many aspects of our criminal justice system may actually exacerbate these problems rather than alleviate them.”

Drug offenses account for 17%, or nearly one in five, of those in state prisons, according to national incarceration data.

It is clear that “too many Americans go to too many prisons for far too long and for no truly good law enforcement reason,” Holder said. “We cannot simply prosecute or incarcerate our way to becoming a safer nation,” he added later in the speech.

Holder is calling for a change in Justice Department policies to reserve the most severe penalties for drug offenses for serious, high-level or violent drug traffickers. He has directed his 94 U.S. attorneys across the country to develop specific, locally tailored guidelines for determining when federal charges should be filed and when they should not.

He also said the Justice Department would work with the Department of Education and other allies “to confront the ‘school-to-prison pipeline’ and those zero-tolerance school discipline policies that do not promote safety,” but instead serve as gateways to the criminal justice system.

“A minor school disciplinary offense should put a student in the principal’s office and not a police precinct,” Holder said.

The attorney general can make some changes to drug policy on his own. He is giving new instructions to federal prosecutors on how they should write their criminal complaints when charging low-level drug offenders, to avoid triggering the mandatory minimum sentences. Under certain statutes, inflexible sentences for drug crimes are mandated regardless of the facts or conduct in the case, reducing the discretion of prosecutors, judges and juries.

Some of Holder’s other initiatives will require legislative change. Holder is urging passage of legislation with bipartisan support that is aimed at giving federal judges more discretion in applying mandatory minimum sentences to certain drug offenses.

“Although incarceration has a role to play in our justice system, widespread incarceration at the federal, state and local levels is both ineffective and unsustainable,” Holder said.

He said legislation supported by Sens. Richard J. Durbin (D-Ill.), Patrick J. Leahy (D-Vt.), Mike Lee (R-Utah) and Rand Paul (R-Ky.) “will ultimately save our country billions of dollars.”

The cost of incarceration in the United States was $80 billion in 2010, according to the Justice Department. While the U.S. population has increased by about a third since 1980, the federal prison population has grown by about 800 percent. Justice Department officials said federal prisons are operating at nearly 40 percent over capacity.

Federal officials attribute part of that increase to mandatory minimum sentences for drugs, including marijuana, under legislation passed in the 1980s. Under the Anti-Drug Abuse Act of 1986, for example, a minimum sentence of five years without parole was mandated for possession of five grams of crack cocaine, while the same sentence was mandated for possession of 500 grams of powder cocaine, law enforcement officials said, pointing to discrepancies that they say have led to higher levels of incarceration in poorer communities.

“Sentencing by mandatory minimums is the antithesis of rational sentencing policy,” American Bar Association lawyer James E. Felman said in testimony three years ago before the U.S. Sen­tencing Commission.

Although the United States is home to 5 percent of the world’s population, almost a quarter of the world’s prisoners are incarcerated in American prisons, according to the Justice Department. More than 219,000 federal inmates are behind bars, and almost half of them are serving time for drug-related crimes.

An additional 9 million to 10 million people cycle through local jails in the United States each year. About 40 percent of former federal prisoners and more than 60 percent of former state prisoners are rearrested or have their supervision revoked within three years after their release, often for technical or minor violations of the terms of their release.

Holder said he has also revised the department’s prison policy to allow for more compassionate releases of elderly inmates who did not commit violent crimes, have served significant portions of their sentences and pose no threat to the public.

Over the next weeks, Holder and his deputies plan to visit cities to promote their prison agenda and point to examples of the type of change the attorney general is advocating.

New legislation in Kentucky, for example, has reserved prison beds for only the most serious criminals, focusing resources instead on community supervision and other alternatives. The state is projected to reduce its prison population by more than 3,000 over the next 10 years, saving more than $400 million, according to Justice Department officials.

Investments in drug treatment for nonviolent offenders and changes to parole policies helped Arkansas reduce its prison population by more than 1,400 inmates, U.S. officials said, and led to a reduction in the prison population of more than 5,000 inmates last year in Texas.

Holder did not announce any changes in the Justice Department’s policy on marijuana, which is illegal under federal law. Two states, Colorado and Washington, legalized marijuana in November. Supporters of the measures argued that hundreds of millions of dollars have been wasted on a failed war against marijuana that has filled American prisons will low-level offenders.

Supporters also contended that decriminalization would bring in hundreds of millions of dollars in tax revenue that could be used for education, health care and other government services.

But the legalization measures directly violate the federal Controlled Substances Act, which prohibits the production, possession and sale of marijuana and classifies marijuana as a Schedule 1 drug, putting it in the same category as LSD and heroin. The Justice Department has not said how it will respond to the measures in Colorado and Washington, leaving state and local officials confused about exactly how to proceed. A Justice Department spokesman said the matter is still under review.