Catholic Church officials say they expect Pope Francis to expand his planned September trip to Philadelphia to include New York City and Washington, D.C.

The Archdiocese of New York, headed by Cardinal Timothy Dolan, is engaged in preliminary planning for a visit, said Joseph Zwilling, a spokesman for the archdiocese.

"We're all very much expecting him to come," Zwilling said. "At this point, we would be more surprised if he didn't come than if he did."

The Vatican announced in November that Francis will visit Philadelphia Sept. 26-27, just after the conclusion of the 2015 World Meeting of Families, expected to draw 10,000 delegates from 150 countries there. The pope's visit -- which organizers said could bring more than 2 million people to the city -- is to include a public Mass on Sept. 27.

Vatican officials have not confirmed the pope will travel to other places in the United States, but they have come close. The pope's visit coincides with the opening of the 70th session of the UN General Assembly, which annually attracts leaders from around the world.

Cardinal Pietro Parolin, the Vatican secretary of state, said last week he expects Pope Francis to include stops in both New York and Washington. Parolin is considered the highest Vatican official under the pope.

Asked if Francis would visit the United Nations in September, Parolin told Catholic News Service in Rome, "I think so, I think so, but no official announcement has been done. But everybody is speaking of that."

The cardinal, asked if the trip also would include Washington, replied, "Of course," then added with a laugh, "but no official confirmation has been given."

Archbishop Bernardito Auza, head of the Holy See's permanent observer mission to the United Nations, has said that if Pope Francis "comes to Philadelphia, he will come to New York."

Zwilling said a visit to New York makes sense for a number of reasons. This year is the 50th anniversary of Pope Paul VI's address to the United Nations in 1965, when he was the first pope to visit the United States.

The renovation of St. Patrick's Cathedral also will be complete or nearly complete by late September, offering a perfect opportunity for the pope to "re-bless" it if he chooses, Zwilling said.

Since being named pope, Francis has demonstrated a knack for spontaneous, unpredictable gestures. Given his focus on society's poor and marginalized, as well as migrants and refugees, it is possible he would want to visit city neighborhoods that struggle with poverty, Zwilling said.

In preliminary in-house discussions, officials at the archdiocese have discussed the idea of the pope visiting an immigration center run by Catholic Charities, he said. All is contingent upon the amount of time Francis would be in New York and what he would want to do, Zwilling said.

Whether a public Mass at Yankee Stadium, Citi Field, Central Park or elsewhere would take place is unclear, officials said, because the pope already has the outdoor Mass scheduled in Philadelphia.

In addition, Fordham University, which is run by the Jesuit order of priests to which Francis belongs and has campuses in the Bronx and Manhattan, "would love for him to visit," university spokesman Robert Howe said.

The pope is not expected to stop in the Diocese of Rockville Centre, and diocesan spokesman Sean Dolan said no preparations are underway. Some of the faithful from Long Island are planning to travel to Philadelphia to see Francis, he said.

As for a stopover in Washington, some church officials think a papal visit is likely, allowing the pope to address a joint session of Congress and meet with President Barack Obama in the White House. The pope's crucial role in brokering the historic re-establishing of ties between the United States and Cuba makes a visit to the nation's capital even more likely, church analysts said.

Other groups across the country are actively campaigning for additions to the papal itinerary.

Bishops in New Mexico have publicly invited him to visit the U.S.-Mexico border. Schoolchildren in Detroit have launched a letter-writing campaign. The faithful in Wisconsin want him to visit a shrine in Green Bay where the Catholic Church says the Virgin Mary appeared to a young girl in 1859.

Cardinal Dolan "has on several occasions invited Pope Francis to come to New York, and Pope Francis has expressed his desire to do so," Zwilling said. "The way Pope Francis has captured the world's imagination so quickly, I think will make this just an unbelievable experience."

In his April 2008 visit to the United States, Pope Benedict XVI came to New York, addressing the UN General Assembly and visiting the Sept. 11 memorial site. The late John Paul II -- an energetic traveler who was on U.S. soil seven times during more than 26 years as pope -- visited New York twice during his papacy, in October 1979 and October 1995. He addressed the UN General Assembly each time.