The U.S. Sentencing Commission voted unanimously Thursday, in favor of shorter federal jail terms for non-violent drug offenders.

The amendment would reduce the average sentence for drug dealers by 11 months or 17 percent.  For instance, a person found guilty of carrying 1 kg (2.2 lbs) of heroin would serve 51 to 63 months in jail rather than 63 to 78 months, reports Reuters.

An estimation made by the commission stated that the amendments would affect around 70 percent of federal drug dealing defendants. It also said that  the sentencing would  reduce the federal prison population by over 6,500 in 5 years.

Almost half of over 216,000 federal prisoners are serving jail term for drug-related crimes. The population of the inmates is around three times the size it was in 1991. The Justice Department spends $6.4 billion annually to maintain prisons, a report in The Washington Times states.

"Our country is slowly but steadily reversing the damage done by the failed, racially biased war on drugs," Jesselyn McCurdy, an American Civil Liberties Union senior legislative counsel, said in a statement.

"The actions taken by the Sentencing Commission today are another positive move toward reducing unnecessarily long sentences that have led to bloated, overcrowded prisons. Our criminal justice system is smarter, fairer, and more humane than it was a year ago, and we need to make sure momentum continues in the right direction," she added.

The decision came in the midst of attempts made by both liberals and conservatives to lessen the prison term for those involved in non-violent drug offences. The commission, however, criticized Attorney General Eric Holder for telling the federal prosecutors to implement the guidelines before they had been approved.

In a statement Holder said the decision by the commission was a "milestone" but added that the Congress needed to do more to ease the "overburdened prison system," reports the Associated Press.

Congress will get the amendment by May 1. If it does not introduce and pass legislation to stop the proposed changes within six months, the amendment will become law with effect from Nov. 1, 2014.