Pope Francis said Monday that he will visit Philadelphia in September 2015, his first trip to the United States since being elected pontiff.
Francis is due to attend the "World Meeting of Families" in Philadelphia, an event held every three years in different cities, where prelates are expected to discuss family issues. Francis will also hold a Mass, likely on the Benjamin Franklin Parkway, which could draw up to a million people.
Last week, more than 10,000 Philadelphia Catholic schoolchildren wrote to Francis asking him to visit. Philadelphia Mayor Michael Nutter said on Monday the event would be the largest in the city's modern history.
Describing Francis' visit, Philadelphia Archbishop Charles Chaput said, "His charisma, presence and voice will electrify the gathering."
The website of the Philadelphia event said the Argentinian pope would visit the city from Sept. 25-27.
The pope has said President Obama and U.S. congressional leaders have invited him to Washington, and that United Nations Secretary-General Ban Ki-moon has asked him to come to New York, the Catholic News Service reported.
He will be the second pope to visit Philadelphia after John Paul II's visit in 1979. The last papal visit to the United State was made by Pope Benedict XVI in 2008.
Francis made the widely expected announcement of his trip at a Vatican conference on family values at which he delivered a robust defense of the heterosexual family unit.
"The family is the foundation of co-existence and a remedy against social fragmentation," he said. "Children have a right to grow up in a family with a father and a mother capable of creating a suitable environment for the child's development and emotional maturity."
The family, added Francis, "is an anthropological fact," adding, "We cannot qualify it based on ideological notions or concepts important only at one time in history."
The pope's comments followed a synod in October at which bishops split over the welcome the Catholic Church should give to gay and unmarried couples.
One of the Vatican sponsors of the event on Monday was the Congregation for the Doctrine of the Faith, run by German Cardinal Gerhard Muller, who is one of the Church's most outspoken conservatives.
Francis' speech came two days after he condemned euthanasia and in vitro fertilization, which he called "the scientific production of a child."
The speeches will go some way to placating U.S. bishops startled by Francis' seeming pullback from the church's hard-line approach to hot-button issues such gay marriage, particularly after he said last year, "We cannot insist only on issues related to abortion, gay marriage and the use of contraceptive methods."
On Monday, a senior U.S. cardinal said Francis needed to choose his words carefully, starting with his now-famous statement in answer to a question about homosexuality: "Who am I to judge?"
That phrase "has been very misused … because he was talking about someone who has already asked for mercy and been given absolution, whom he knows well," said Cardinal Francis George, who steps down as archbishop of Chicago on Tuesday.
"That's entirely different than talking to somebody who demands acceptance rather than asking for forgiveness," George told the website Crux.
"Does he not realize the repercussions? Perhaps he doesn't," George said. "The question is why he doesn't clarify" the statements?
Next year's "World Meeting of Families," at which the pope will likely discuss family issues, will come just weeks before a key synod that will pick up on the divisive themes debated in Rome in October.