Pope Leo XIV has promised to make the Catholic Church a balm for the world’s “dark nights”, as he celebrated his first mass as pontiff less than 24 hours after being elected.

Sixty-nine-year-old Leo, the former Cardinal Robert Prevost and the first American pope, delivered the Mass on Friday, flanked by cardinals in the Vatican City’s Sistine Chapel.

The new head of the Catholic Church was elected by fellow cardinals on Thursday, following Pope Francis’s death, and has become the first US pontiff in the church’s 2,000-year history.

Leo, who now leads the world’s 1.4 billion Catholics, acknowledged that the Christian faith is sometimes “considered absurd” and the preserve of “the weak and unintelligent”.

“A lack of faith is often tragically accompanied by the loss of meaning in life, the neglect of mercy, appalling violations of human dignity, the crisis of the family and so many other wounds that afflict our society,” he said at the mass, adorned in simple white and gold clothes.

He also warned that Jesus cannot be “reduced to a kind of charismatic leader or superman”.

“This is true not only among non-believers, but also among many baptised Christians, who thus end up living, at this level, in a state of practical atheism,” he said.

The new pontiff said he would seek to serve as the “faithful administrator” for the Church as a whole.

Leo will be formally installed as pope at a mass on May 18 and will preside over his first general audience on May 21, the Vatican said, with world and religious leaders invited to his formal launch of the papacy.

Pope Francis’s inauguration in 2013 attracted a crowd of about 200,000 people.

The new pope will also leave senior Vatican officials in their roles for the time being, giving him time to decide before making appointments, the Vatican said.

The pope was elected at the end of a two-day conclave that wrapped up on Thursday evening when white smoke billowed from the chimney of the Sistine Chapel.

Francis, who died last month at the age of 88, leaves Leo to inherit a number of major challenges, ranging from a budget shortfall to divisions about whether the Church should be more welcoming towards the LGBTQ community and divorcees, and should let women play a greater role in its affairs.

Leo was born in Chicago but spent two decades as a missionary in Peru.

Before his election, US cardinals were largely written off as papal contenders because of a widespread assumption that the global Church could not be run by a superpower pope.

However, since Leo also holds Peruvian citizenship, it is understood that he has knowledge of both the West and the Global South.