OKLAHOMA CITY (AP) — Barack Obama is set to become the first sitting US President to visit the inside of a federal prison as part of a push to change the country’s justice system.

Obama will meet separately Thursday with law enforcement officials and nonviolent drug offenders who are paying their debt to society at a medium-security prison for male offenders in the state of Oklahoma.

From shortening the prison sentences of nearly four-dozen non-violent drug offenders to advocating the reduction, or outright elimination, of severe mandatory minimum sentences, Obama has argued forcefully this week for an alternative to the continued lengthy incarceration of people convicted of crimes he said did not fit the punishment.

Obama has said that overly harsh prison sentences, particularly for nonviolent drug crimes, are to blame for doubling the prison population in the past two decades. Half a million people were behind bars in 1980, a figure that has since quadrupled to its current total of more than 2.2 million inmates.

“Mass incarceration makes our country worse off, and we need to do something about it,” Obama said in a recent speech.

White House press secretary Josh Earnest said “unique steps” will be taken to protect Obama during the visit. He did not elaborate.

Secret Service spokesman Brian Leary said “comprehensive security screening” will be conducted, calling it standard practice.

Danny Spriggs, a former deputy director of the U.S. Secret Service, which provides the president’s security, said Obama’s prison tour likely will be limited to critical areas, and those areas will be roped off so that access is given only to the warden and immediate staff so they can explain what happens there daily.

“Those hallways will be clear,” Spriggs said.

Earlier this week, Obama commuted the sentences of 46 nonviolent drug offenders, 14 of whom had been serving life in prison.

“If you’re a low-level drug dealer, or you violate your parole, you owe some debt to society. You have to be held accountable and make amends,” Obama said in a speech this week. “But you don’t owe 20 years. You don’t owe a life sentence. That’s disproportionate to the price that should be paid.”

Obama said taxpayers are the ones left to pay the $80 billion annual cost of locking up people who otherwise could be in rehabilitative programs for less than the cost of incarceration. Or they could be workers paying taxes, or be more involved in their children’s lives, or be role models and leaders in their communities.

Obama has also called for restoring voting rights to felons who have served their sentences, and said employers should “ban the box” that asks job applicants about their criminal histories.

The US President has expressed hope that Congress will send him legislation to address the issue before he leaves office in 18 months, given the level of interest in the issue among Republican lawmakers and presidential candidates.

Republican Senator Rand Paul, a 2016 presidential contender, is pushing to restore voting rights to nonviolent felons who have served their sentences. Another Republican hopeful, New Jersey Governor Chris Christie, was giving a speech Thursday calling for changes that in part would give nonviolent drug offenders a better chance at rebuilding their lives.