President Obama calls the death penalty "deeply troubling," but he still has not changed his position in favor of using it for particularly heinous crimes.

In an interview Thursday with the Marshall Project, Obama said, "At a time when we’re spending a lot of time thinking about how to make the system more fair, more just, that we have to include an examination of the death penalty in that.”

Obama has been said to be reviewing the death penalty for more than a year, and the White House months ago mentioned that there was a Justice Department review in progress.

"This is something that I've struggled with for quite some time," Obama said. "There are certain crimes that are so beyond the pale that I understand society's need to express its outrage.

"I've not been opposed to the death penalty in theory, but in practice it's deeply troubling," he said.

He cited cases in which people convicted were later proven innocent and noted that there had been cases in which the application of the death penalty had "not been swift and painless but gruesome and clumsy."

The Marshall Project is a nonprofit news organization that focuses on the American criminal justice system. Its editor-in-chief, Bill Keller, conducted the interview with the president.

Pope Francis called for an end to the death penalty in his recent address to Congress. “It’s fair to say the president’s views are influenced by statements that are made by the pope,” White House press secretary Josh Earnest told reporters. But Earnest said that Obama was not ready to change his position.

Charles J. Ogletree Jr. — a prominent death penalty opponent who was a law professor of the president and first lady Michelle Obama when both were students at Harvard Law School — has also urged Obama to alter his position. "He's not there yet, but he's close, and needs some help," Ogletree said in an interview with The Washington Post earlier this year.

Obama raised expectations about a possible change in May 2014, after a prisoner in Oklahoma regained consciousness and writhed and groaned in pain after receiving a lethal injection. Obama called that situation "deeply troubling" and said it highlighted broader issues with capital punishment in the United States, including people sentenced to death who turned out to be innocent and issues of racial bias.

"All these I think do raise significant questions about how the death penalty is being applied," he said during a news conference in the Rose Garden.

While a majority of Americans favor the death penalty, that number has steadily fallen over the past two decades.

As a declining number of states carry out a shrinking number of executions each year, the federal government also has the ability to seek death sentences. Earlier this year, the government sought and won a death sentence for Dzhokhar Tsarnaev, one of the Boston Marathon bombers. However, the federal government has not put an inmate to death since 2003 and is not carrying out any executions while the Justice Department review is ongoing.