U.S. President Barack Obama has met Pope Francis at the Vatican where they spoke about global conflicts and inequities in global wealth.

The two leaders smiled when they shook hands, posing for photographs while sitting at a table facing each other and spoke later for 52 minutes.

The meeting had a special significance due to the United States having 78.2 million people identifying themselves as Catholics, the largest religious group in the country comprising 25 percent of the population.[

Thursday's audience was the second time that the Vatican had received Obama, after an audience with Pope Benedict XVI on July 10, 2009.

Obama's meeting with Francis took place at a time of some tensions between the Catholic Church and his administration relating to health care reform that relates to rules on mandatory health care coverage of sterilization, contraception, and abortion.

Another issue that the Catholic Church disagrees with, is same-sex marriage.

After the meeting the Vatican released a statement saying that the two leaders discussed "current international themes."

It said they expressed the hope that "in areas of conflict there would be respect for humanitarian and international law and a negotiated solution between the parties involved."

Obama said at press confernce later that he had invited Francis to visit the United States.

The two world leaders greeted each other with a smile and a handshake, and posed for pictures before sitting down across a table from each other.

Obama is the ninth US President to make ​​an official visit to the Vatican.

WOODROW WILSON

The first, Woodrow Wilson, was received by Pope Benedict XV after the end of the First World War.

The next audience for a sitting president came thirty years later, when Blessed Pope John XXIII, received President Dwight Eisenhower in 1959.

John Fitzgerald Kennedy, who was the first, and to date the only, Catholic president, met with Pope Paul VI in 1963. Paul VI later received three other presidents, meeting twice each with both Lyndon Johnson and Richard Nixon, and once with Gerald Ford.

The visit of Blessed John Paul II to Washington in 1979, when he met Jimmy Carter, was the first visit of a pope to the White House.

It was also the first of many meetings with American Presidents during his long pontificate.

During Ronald Reagan's presidency, diplomatic relations between the Holy See and the United States were established at the highest level.

George Bush, Sr., met twice with Pope John Paul, both times at the Vatican. President Bill Clinton welcomed Pope John Paul to the United States three times, and travelled once to the Vatican.

George W. Bush became the first President to meet two different Popes while in office, meeting three times each with Pope John Paul II and Pope Benedict XVI.

He is the only President to be received by a Pope at the summer papal residence of Castel Gandalfo, in 2001.

While president, George W. Bush attended the funeral of John Paul II, along with former presidents George H. W. Bush and Bill Clinton; both Cardinal Joseph Ratzinger and Cardinal Jorge Bergoglio (later Pope Benedict XVI and Pope Francis), were also present.

President Obama's first meeting with a pope occurred when he visited Rome in 2009.