Pope Francis talks with journalists on the plane during the flight Monday from Manila to Rome. (Ettore Ferrari/EPA)

Pope Francis confirmed Monday that his first visit to the United States since being named leader of the world’s 1.2 billion Catholics will include trips to Washington and New York City in late September, as well as a previously announced stop in Philadelphia.

Francis, named pope in March 2013, confirmed the three-city swing during an hour-long news conference on a flight back to the Vatican from a tour of Asia. The pontiff said that in Washington, he will canonize Junípero Serra, the Spanish Franciscan friar who began the California mission system in 1769, and will celebrate Mass at the Basilica of the National Shrine.

In New York, he will address the U.N. General Assembly, where world leaders will gather for a summit on sustainable development, he said.

Francis said he wished he could go to Mexico to enter the United States from its southern border “as a sign of brotherhood and of help to the immigrants,” according to a Vatican transcript.

But the pope joked that “war could break out” if he did not also visit Mexico’s Basilica of Our Lady of Guadalupe, adding, “there will be time to go to Mexico later on.”

The Vatican in November announced a papal visit to Philadelphia for a major meeting on family issues that runs Sept. 22-27.

House Speaker John A. Boehner (R-Ohio) and Minority Leader Nancy Pelosi (D-Calif.), both Catholic, invited the popular Francis last March to become the first pope to address Congress. Pope Benedict XVI visited the White House in 2008.

A Vatican spokesman, Father Thomas Rosica of Canada, cited a Vatican transcript and said all details are not finalized among the archdioceses of the three cities, the U.S. Conference of Catholic Bishops and the U.S. government.

Two Catholic news organizations reported Sunday that the church’s representative to the United Nations, Archbishop Bernardito Auza, said in the Philippines that a papal delegation will make an organizational visit to the United States to flesh out the itinerary late next month.

The Catholic News Agency and EWTN reported that planners were considering having Francis land Sept. 22 in Washington, with travel Sept. 24 to New York to address the United Nations and possibly stop at Ground Zero, the site of the Sept. 11, 2001, terrorist attacks. Philadelphia would be the last stop, according to reports.

Pope Francis leads a huge public Mass for a rain-drenched crowd of millions in the Philippine capital. (Reuters)

The CNA reported that Francis said he hoped to visit three Latin American countries this year and next — Bolivia, Ecuador and Paraguay in 2015 and Argentina, Chile and Uruguay in 2016 — and also hoped to visit the Central African Republic and Uganda late this year.