The United States plans to free nearly 6,000 prisoners — the largest ever one-time release of federal inmates — in an effort to reduce overcrowding and ease the punishment for drug crimes.

The massive release, announced on Tuesday by the Department of Justice (DOJ), will take place over a four-day period from October 30 to November 2.

"It's a great first step in addressing a very longstanding problem of over incarceration," said Gary Feldon, chair of the American Bar Association's Section on Civil Rights and Social Justice Criminal Justice. "It's indicative of a general mood in the country on both sides of the aisle, where there's real interest in remedying over incarceration."

The releases were set in motion by the US Sentencing Commission, which voted unanimously last year to reduce federal drug sentences by an average of two years. The decision came after nearly two years of public hearings that included testimony from DOJ officials, advocacy groups, and experts.

The lengthy process led to rebalanced federal sentencing guidelines that decrease the weight of drug offenses and encourage early release of prisoners serving long terms for drug-related crimes.

The impact of the new policy could be huge. The approximately 6,000 released prisoners are just the first batch of what is poised to be the nation's largest-ever prison release program. When the commission announced its new "Drugs Minus Two" policy last year, it estimated the changes could result in early releases for as many as 46,000 of the approximately 100,000 drug offenders in federal custody.

The timeline for those releases remains unclear, but Sentencing Commission spokesman Matt Osterrieder said that an additional 8,550 prisoners could become eligible for release within the next year.

The DOJ emphasized on Tuesday that the new policy does not let prisoners off the hook. "Even with the Sentencing Commission's reductions, drug offenders will have served substantial prison sentences," Deputy Attorney General Sally Yates told the Washington Post. "Moreover, these reductions are not automatic."

Though the number of released prisoners is unprecedented, each case still requires the approval of a judge. On average, federal judges have been issuing about 70 reduced sentences per week, the DOJ estimated.

The release program comes as both Democrats and Republicans are increasingly focused on ending mass incarceration. President Barack Obama recently became the first sitting president to meet with federal prisoners as part of VICE documentary, and he has vowed to make criminal justice reform a key priority during the last leg of his presidency.

Congress is also considering the first serious bipartisan criminal justice reform bill in decades. The bill has support from a wide range of stakeholders — from the ACLU to the Koch Brothers — and would cut the prison terms for drug offenders who face so-called mandatory-minimum sentences.