EL RENO (Oklahoma) • US President Barack Obama, who wrote in his memoir about using marijuana and cocaine as a youth, became the first sitting president to tour a federal prison on Thursday and met drug convicts, saying he could have been in their place if not for the advantages he had growing up.

Mr Obama spoke with inmates and toured El Reno prison, which holds 1,300 inmates, 146 per cent of its capacity.

He vowed to work with wardens and corrections officers to address overcrowding, a piece of his administration's wide-ranging criminal justice reform agenda.

Mr Obama walked down the prison's dimly lit grey halls and stood at the door of Cell 123, Block B, noticing its two occupants' sparse supplies: brown uniforms, mesh laundry bags, dish soap and a few books.

Six non-violent drug offenders shared their stories with Mr Obama. Their discussions will air on HBO's "Vice" documentary programme in September.

Speaking to reporters later, Mr Obama reflected: "These are young people who made mistakes that aren't that different from mistakes I made. The difference is they did not have the support structure, the second chances, the resources that would allow them to survive these mistakes."

More than 1.5 million Americans were in state or federal prisons at the end of 2013, according to the Bureau of Justice Statistics. African-Americans, 15 per cent of the US population at that time, accounted for about a third of its prisoners.

Mr Obama said the criminal justice system should do a better job of discerning between young drug offenders from poor backgrounds and hardened, violent criminals.

"We have to consider whether this is the smartest way for us to control crime and rehabilitate individuals," he added.

REUTERS