US President Barack Obama at the El Reno Federal Correctional Institution in El Reno, Oklahoma, July 16. AP WASHINGTON (Reuters) — The US Justice Department is set to release about 6,000 prisoners early in the largest one-time release of federal inmates, The Washington Post reported Tuesday.

The release, scheduled for between October 30 and November 2, is an effort to reduce overcrowding and provide relief to drug offenders who received harsh sentences over the past three decades, the newspaper said.

The inmates will be set free by the department's Bureau of Prisons. Most will go to halfway houses and home confinement before being put on supervised release, The Post said.

A Justice Department spokesman was not immediately available for comment.

The early release follows actions by the US Sentencing Commission, an independent agency that sets sentencing policies for federal crimes. The panel reduced the potential punishment for drug offenders last year and made the change retroactive.

The commission's action is separate from an effort by US President Barack Obama to grant clemency to some nonviolent drug offenders, an initiative that has resulted in the early release of 89 inmates.

The sentencing panel estimated that its change in guidelines could result in 46,000 of the roughly 100,000 drug offenders in federal prison qualifying for early release. The 6,000 figure is the first batch in that process, The Post said.

There are 206,000 inmates in federal prisons, up from about 25,000 in 1980, according to the Bureau of Prisons' website. There were a total of 1.56 million inmates in federal and state prisons at the end of 2014, according to Department of Justice figures.

The drumbeat for sentencing reform has come as US crime rates have drastically declined over the past two decades. US senators last week proposed a plan to reform criminal justice, aiming to scrap sentencing laws that lead to overcrowding.

The Drug Policy Alliance, an advocacy group, welcomed the move but said it was no substitute for a systemic makeover.

"Congress still needs to pass comprehensive criminal-justice reform," Michael Collins, the group's police manager, said in a statement.

Reporting by Ian Simpson. Editing by Sandra Maler.