President Obama announced Monday that he is commuting the prison sentences of 46 mostly nonviolent drug offenders, saying the "punishment didn't fit the crime."

"I wanted to personally inform you that I will be granting your application for commutation," Obama wrote in a letter sent to each of the 46 men and women. "I am granting your application because you have demonstrated the potential to turn your life around. Now it is up to you to make the most of this opportunity. It will not be easy, and you will confront many who doubt people with criminal records can change. Perhaps even you are unsure of how you will adjust to your new circumstances."

Because of changes to sentencing guidelines, many of the prisoners would have already served their time if they were convicted with the same crime today, Obama said. Although, 13 of the prisoners were sentenced to life in prison.

"These men and women were not hardened criminals, but the overwhelming majority had been sentences to at least 20 years. Fourteen of them had been sentenced to life for nonviolent drug offenses. So, their punishments didn't fit the crime," Obama said in a video posted to the White House Facebook page. "I believe that at its heart, America is a nation of second chances. And I believe these folks deserve their second chance."

Obama said the commutations were part of a broader effort by his administration to enact comprehensive criminal justice reform. With Monday's announcement, Obama has now issued 89 commutations, the majority to nonviolent drug offenders sentenced under guidelines established in the 1980s, according to the Washington Times. That's more commutations than any other president since Lyndon B. Johnson, according to CNN.

The commuted sentences are expected to end in November, as officials need a several month transition period to make arrangements in halfway houses and similar facilities. Prisoners will then be supervised by probation officers and subject to various conditions set during their original sentencing, including drug testing in some cases.

A commutation only reduces a sentence, whereas a presidential pardon also erases a criminal conviction.

Obama is expected to further discuss criminal justice reform later this week, including plans to reduce overcrowding in prisons, review sentencing laws and reducing punishments for non-violent crime, according to CNN.

Relaxing federal sentencing guidelines is supported by even the staunchest Republicans, such as libertarian-minded Sen. Rand Paul of Kentucky, who is running for president, and billionaire donors Charles and David Koch, two of the most influential people in politics.

"Over the last few years a lot of people have become aware of the inequities in the criminal justice system," Obama said in the video. "Right now, with our overall crime rate and incarceration rate both falling, we're at a moment when good people in both parties, Republicans and Democrats, and folks all across the country are coming together around ideas to make the system work smarter, make it work better, and I'm determined to do my part wherever I can."