Pope Francis announced on Monday he would visit the United States next year, his first trip there as leader of the 1.2 billion-member Roman Catholic Church.

The official confirmation of the trip was keenly awaited in the United States after months of speculation.

Francis told an inter-religious conference on marriage he would go to Philadelphia in September for the Roman Catholic Church's World Meeting of Families, an international gathering.

Archbishop Charles Chaput of the Archdiocese of Philadelphia was in Rome when the announcement was made and issued a statement saying he was "overjoyed" at the prospect of the pope's attendance at the event.

"A hallmark of his papacy has been a keen focus on the many challenges that families face today globally. His charisma, presence and voice will electrify the gathering," Chaput said.

"As I've said many times before, I believe that the presence of the Holy Father will bring all of us - Catholic and non-Catholic alike - together in tremendously powerful, unifying and healing ways," he said.

The trip is also expected to include stops at the White House and Congress in Washington and the United Nations in New York, but the pope did not mention those places in his address.

Catholic officials in Philadelphia have said a papal Mass would draw up to a million people.

He would be the fourth pope to visit the United States, the archdiocese said. Pope Benedict XVI came to America in 2008 and Pope John Paul II in 1979.

The World Meeting of Families, set to be held September 22-27, 2015, meets every three years. It is intended to strengthen the bonds of family worldwide and highlight the value of family bonds to society, the archdiocese said.

Next year would be its first meeting in the United States.

Details of the pope's visit were expected to be made public in the spring, according to the archdiocese.

He is likely to attend a Festival of Families on September 26 and a Mass the following day, it said.

The pope is due to visit Turkey and European institutions in Strasbourg, France, in two separate trips this month.

In January, he travels to the Philippines and Sri Lanka, making his second trip to Asia.

(Reuters)