By Dan Merica, CNN

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(CNN) -– American atheists welcomed Pope Francis’ comments that God redeems nonbelievers, saying that the new pontiff's historic outreach is helping to topple longstanding barriers.

“The Lord has redeemed all of us, all of us, with the Blood of Christ: all of us, not just Catholics. Everyone,” the pope told worshipers at morning Mass on Wednesday. “‘Father, the atheists?’ Even the atheists. Everyone!”

Francis continued, “We must meet one another doing good. ‘But I don’t believe, Father, I am an atheist!’ But do good: we will meet one another there.”

Roy Speckhardt, executive director of the American Humanist Association, said that although he has been skeptical of Francis' outreach to the nonreligious, he welcomed Wednesday’s comments.

“I gather from this statement that his view of the world's religious and philosophical diversity is expanding,” Speckhardt said. “While humanists have been saying for years that one can be good without a god, hearing this from the leader of the Catholic Church is quite heartening."

He continued, “If other religious leaders join him, it could do much to reduce the automatic distrust and discrimination that atheists, humanists, and other nontheists so regularly face. “

Francis’ comments received a great deal of attention on social media, with a number of people asking whether the Catholic leader believes that atheists and agnostics go to heaven, too.

On Thursday, the Vatican issued an “explanatory note on the meaning to ‘salvation.'"

The Rev. Thomas Rosica, a Vatican spokesman, said that people who aware of the Catholic church “cannot be saved” if they “refuse to enter her or remain in her.”

At the same time, Rosica writes, “every man or woman, whatever their situation, can be saved. Even non-Christians can respond to this saving action of the Spirit. No person is excluded from salvation simply because of so-called original sin.”

Rosica also said that Francis had “no intention of provoking a theological debate on the nature of salvation,” during his homily on Wednesday.

Although the pope's comments about salvation surprised some, bishops and experts in Catholicism say Francis was expressing a core tenet of the faith.

"Francis was clear that whatever graces are offered to atheists (such that they may be saved) are from Christ," the Rev. John Zuhlsdorf, a conservative Catholic priest, wrote on his blog.

"He was clear that salvation is only through Christ’s Sacrifice. In other words, he is not suggesting – and I think some are taking it this way – that you can be saved, get to heaven, without Christ."

Chad Pecknold, an assistant professor of theology at the Catholic University of America, agreed with Zuhlsdorf, pointing out that the pope’s comments came on the Feast of Saint Rita, the Catholic patron saint of impossible things.

“The remarks about atheists show that there is even a saint for atheists,” Pecknold said. “Including all of humanity, on this day especially, remarks like that are almost called for.”

“To stress that the gospel redeems all people, including atheists, is the teaching of the church,” he added. “This is an objective fact that the church believes.”

Greg Epstein, the humanist chaplain at Harvard University, said Francis' comments reflect “the interfaith and inter-community work many of us nontheists are dedicated to.”

That said, Epstein hopes that lay Catholics are listening.

“I hope Catholics, and all people hearing the pope's statement, will recognize that his words about atheists need to symbolize much more than just a curiosity or an exception to the rule,” Epstein said. “If someone thinks there are only a few atheists out there doing good just like Catholics do, that's a major misunderstanding that can lead to prejudice and discrimination.”

The pope’s comments come a few months after he told worshipers that Catholics should be close to all men and women, including those who don’t belong to any religious tradition.

"In this we feel the closeness also of those men and women who, while not belonging to any religious tradition, feel, however the need to search for the truth, the goodness and the beauty of God, and who are our precious allies in efforts to defend the dignity of man, in the building of a peaceful coexistence between peoples and in the careful protection of creation,” Francis said shortly after his election as pope in March.

Even atheists like David Silverman, president of American Atheists, who has had an antagonistic relationship with the Catholic church, welcomed the pope’s remarks.

“While the concept of Jesus dying for atheists is wrong on many levels (especially given that Jesus himself promised hell for blasphemers), I can appreciate the pope's `good faith' effort to include atheists in the moral discussion,” Silverman said.

“Atheists on the whole want no part in Catholicism, of course, but we are all interested in basic human rights.”