At the NAACP conference in Philadelphia Tuesday, President Obama will make the case for changes to the criminal justice system to eliminate racial disparities in sentencing and unduly harsh mandatory-minimum sentences for nonviolent offenders, White House officials said.

Obama also will argue that such an approach will leave more resources to address violent crime and that second chances are an integral part of the American ideal.

Obama's 28th visit to Pennsylvania as president comes the day after he commuted the sentences of 46 drug offenders serving long federal sentences, thus doubling the number of nonviolent criminals granted clemency during his administration.

"These men and women were not hardened criminals," Obama said Monday in a Whte House video release. He said 14 of them had been given life sentences for nonviolent drug crimes. "So their punishments didn't fit the crime," the president said.

"I believe that at its heart, America is a nation of second chances," Obama continued, "and I believe these folks deserve their second chance."

Mandatory minimums have disproportionately affected blacks and Latinos, and there is a developing bipartisan consensus to reform sentencing guidelines and to smooth out disparities in punishment. Several Republican presidential candidates, including Kentucky Sen. Rand Paul, have called for changes in the way the law treats nonviolent offenses.

At the NAACP national conference in the Convention Center, Obama will call on Congress to act on changes this year, the White House said.