The head of the Church of Jesus Christ of Latter-day Saints met with a pope for the first time on Saturday, an event that reportedly followed decades of behind-the-scenes relationship building between denominations whose leaders share a concern over secularism.

Pope Francis and President Russell. M Nelson – both men who hold offices of profound spiritual significance for their faiths – met for 33 minutes at the Vatican to discuss the shared priorities of protecting religious rights, traditional family values and young people and opposing secularism, according to the Mormon Church-affiliated Deseret News.

The visit comes a day before Nelson was to dedicate the first Mormon temple in Rome.

There are about 16 million Mormons in the world, compared with more than 1.1 billion Catholics.

However, in a chaotic era when many people are leaving organised religion, leaders of the two denominations share goals, including responding together to disasters and poverty and promoting traditional families and involvement with Christian institutions.

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“We talked about our mutual concern for the people who suffer throughout the world and want to relieve human suffering,” Mr Nelson told his church’s news website.

“We talked about the importance of religious liberty, the importance of the family, our mutual concern for the youth of the Church, for the secularisation of the world and the need for people to come to God and worship Him, pray to Him and have the stability that faith in Jesus Christ will bring in their lives.”

The two groups work together on relief efforts in 43 countries.

“What a sweet, wonderful man he is,” Mr Nelson said of Francis, the Mormon Church news site reported. “And how fortunate the Catholic people are to have such a gracious, concerned, loving and capable leader.”

The Vatican put out no detailed statement about the meeting Saturday, except to include it on the list of people and groups who had audiences with the Pope that day.

The meeting and the existence of the new temple are especially significant for Mormons, said Kathleen Flake, a historian of American religion and an expert on the Latter-day Saints.

The church teaches that it isn’t just generically “Christian” but is the authentic restoration of Jesus’s church.

Establishing the temple in Rome, a centre of global Christianity, and the meeting with the pope give credibility to the Mormon Church as fully Christian, Ms Flake said. That’s important for a group still fighting for acceptance.

In the United States, for example, 97 percent of Mormons consider themselves Christian, compared with just more than half of US adults who recognise Mormonism as a Christian faith, according to a 2016 analysis by the Pew Research Centre.

Asked to volunteer one word that best describes the group, Pew found, the most commonly offered response by non-Mormons was “cult”.

Ms Flake said it was significant that the visitors’ centre of the new temple in Rome features a dramatic Christus sculpture along with sculptures of the 12 apostles.

“There’s a resonance there. It’s a claim...to replicate those statutes, in that place, there’s nothing else it can be. It’s symbolically an assertion of their claim to be the restored Church of Jesus Christ with its apostolic authority,” she said.

Mr Nelson and Pope Francis, she said, are unique. “Are there any other men but those two who believe they stand in the shoes of St. Peter?”

According to the Deseret News, Francis gave Nelson two gifts: some of his writings on the family and on the Islamic faith.

Nelson gave the pope a Christus statue – an image common in the Church of Jesus Christ of Latter-day Saints – and a copy of a core 1995 church document on the family.

Other high-ranking Mormon Church leaders have met with top Catholic leaders in the past, including Henry B Eyring, whose title was the first counselor in the First Presidency. That happened in 2014 when he and Francis spoke at a Vatican conference about marriage, the Deseret News wrote Saturday.

The news site noted that a meeting between men in these positions “would have been unimaginable to leaders and members in both churches” until at least the 1960s, when followers officially were told to limit interactions with other faiths, including weddings and funerals.

But behind-the-scenes connections were happening, the Deseret News reported, and have intensified in the past decade.

The Mormon president, the news site reported, would go in the 1950s to Salt Lake City’s Holy Cross Hospital – which is Catholic-run – “under the guise of visiting a Latter-day Saint patient, then slip into the office of Bishop Duane G Hunt.

They used their private sessions to talk about community issues and the tensions between their members in Utah,” said Monsignor J Terrence Fitzgerald, a Salt Lake City priest interviewed by the site.

Pope Pius XII addresses American troops at the Vatican in 1944 during World War II

“The Catholics were trying to get the Latter-day Saints not to bad-mouth the Catholics at every conference,” Mr Fitzgerald said. “And the Latter-day Saints were trying to get the Catholics to put in a good word for them on the national level.”

Interfaith relations opened significantly with the Second Vatican Council, a major meeting of the Catholic Church in the 1960s.

Both sides have become more open and, in the United States especially, have shared the cause of protecting traditional religious values in public life, such as government-affiliated faith groups’ choice not to offer health benefits to same-sex couples or to place foster or adopted children in their homes.

Leaders of both faith groups have warned about liberalising changes in sexuality, reproductive technology and gender norms and about a decrease in people’s firm belief in God.

“Secularism is prevalent in many Western countries, and many people have lost their faith in Jesus Christ,” Latter-day Saint presiding bishop Gérald Caussé told the Deseret News. “And to have all Christian faiths join together and defend our values is important.”

In Utah, the two communities have developed strong relations in recent decades, the church’s news release said on Saturday.