WASHINGTON — Hill leaders have invited Pope Francis to address a joint session of Congress during his expected visit to the United States next year.

Francis, who marked his first anniversary as leader of the world’s 1.2 billion Catholics Thursday, is reportedly planning to visit the United States to attend a global conference on families scheduled for late September 2015 in Philadelphia. The trip has not been confirmed, officials with the Vatican and the U.S. Conference of Catholic Bishops said Thursday.

House Speaker John Boehner, R-Ohio, issued the invitation as the constitutional officer of Congress, the position that formally invites the president each year to give the State of the Union address. He did so on behalf of House and Senate leaders; minutes after the announcement, House Minority Leader Nancy Pelosi, D-Calif., said she was pleased to join in making the invitation.

Boehner, however, initiated the idea, aides said.

“This is Francis’s one-year anniversary, and John Boehner is Catholic, and so he’s mindful of that,” said Ed Morrissey, a popular conservative commentator and blogger with HotAir.com, and an active Catholic. “But it’s just a measure of how much impact this particular pope is having – everyone wants him there. Who needs it more than Congress, right?”

The Rev. Gerald Fogarty, a historian of Christianity at the University of Virginia who has written on papal visits, said he believed it was the first time a pope has been invited to Congress. Other popes have visited the White House, including most recently Pope Benedict XVI, who came at the request of President George W. Bush in 2008.

The United States did not have diplomatic relations with the Vatican until 1984. “Our country has a history of anti-Catholicism,” said Sister Mary Ann Walsh, spokeswoman for the bishops’ conference.