Just as they hinted for months last year that Pope Francis would visit Philadelphia this September, his aides now hint that he might visit a children's hospital or juvenile detention facility here, but won't confirm it.

Francis told an airborne news conference Monday that he hoped to visit New York City and Washington in the days leading up to his appearances at the World Meeting of Families from Sept. 22 to 27. It was the first time he had spoken publicly of visiting the other cities, but the Holy See has yet to confirm any such plans.

The pontiff made his remarks on a flight to Rome following a visit to Sri Lanka and the Philippines. During the flight he surprised reporters by saying Catholic couples might consider limiting the size of their families.

"God gives you methods to be responsible," he said. "Some think that - excuse the word - that in order to be good Catholics, we have to be like rabbits. No."

He nevertheless affirmed the church's objection to artificial means of birth control, and protested what he called efforts by some wealthy Western nations to impose views of "gender theory" and family planning in poorer parts of the world. He called that "ideological colonization."

On Sunday, the Catholic News Agency reported that Archbishop Bernardito Auza, the Vatican's permanent observer to the United Nations, had said in an interview before Monday's flight that Francis' Philadelphia sojourn would likely include "a visit either to a children's hospital or a juvenile prison."

Both the Archdiocese of Philadelphia and Auza's office in New York said Monday that the Vatican had not confirmed any such plans.

"Those are thoughts and plans, but there is no official confirmation," a woman at Auza's office said. "That will come from the Vatican press office. Before that, we cannot say."

Archdiocesan spokesman Ken Gavin said in a statement that "nothing is confirmed at this time for the schedule" outside of the World Meeting events. Mark McDonald, Mayor Nutter's spokesman, said he was unaware of any plans for the pope to visit other parts of the city.

Francis is already committed to take part in the World Meeting's "Festival of Families" Sept. 26 on the Benjamin Franklin Parkway and to celebrate Mass at the foot of the Philadelphia Museum of Art the next morning. Both events are expected to draw enormous crowds.

Sponsored by the Pontifical Council for the Family, the World Meeting is a triennial gathering that draws Catholics from around the world to learn and celebrate their church's teachings about family and sexuality.

The 2015 World Meeting, hosted by the Philadelphia Archdiocese, will include a four-day congress at the Convention Center before the festival and Mass.

The Catholic News Agency, based in Colorado, said Monday that Auza had told its reporter that a papal visit to a youth prison or children's was "likely," editor Michelle Bauman said, but that these were "just scenarios."

Auza is helping to organize Francis' visit to the United States, which will be his first to this country since his election in March 2013.

Bauman said she did not know if Auza, who is Filipino, had traveled with Francis to the Philippines. On Sunday, Francis confirmed other details of his U.S. visit that Auza had provided to the news agency, suggesting that Auza's remarks represented the pope's intentions.

Both Francis and Auza said he might visit the United Nations, St. Patrick's Cathedral, and the World Trade Center in New York, and the Capitol, the White House, and the Basilica of the National Shrine of the Immaculate Conception in Washington. The New York and Washington visits would take place before the visit to Philadelphia.

The National Catholic Reporter also reported that Francis said Monday that his trip would probably not include a visit to Mexico or the West Coast.

While in Washington, Francis said, he may formalize the canonization of Junipero Serra, an 18th-century missionary in California, which then was part of the Viceroyalty of New Spain.

Another large public Mass in the United States outside of the World Meeting is not expected, according to Auza.

"Our plan is not to have a huge Mass outside of Philadelphia, because the focus will really be Philadelphia, because the pope is going to the United States for the World Meeting of Families," he told CNA.