BARCELONA, Spain (AFP) — Pope Leo XIV on Wednesday said Christians could not consider themselves such if they “promote war” — a thinly veiled reference to United States (US) President Donald Trump’s administration.

In a homily at Barcelona’s Sagrada Familia basilica, Leo also appeared to refer to migration, saying Christians could not “abandon… those who flee from misery”.

“We cannot believe in Jesus and promote war. We cannot believe in Jesus and kill the innocent,” the pope said in front of thousands of worshippers including Spanish King Felipe VI and his wife Queen Letizia.

Leo has labelled “outdated” the concept of a “just war” put forward by Washington in the context of the war against Iran initiated by the US and Israel.

The Trump administration has repeatedly justified its attack on Iran as a way to prevent the country from developing a nuclear weapons capability.

US Vice President JD Vance, a Catholic convert, has used the “just war” argument and has urged the pope to be “careful” on theological matters.

The pope has been a high-profile critic of the Middle East war and has called for a “respectful welcome” for migrants as well as measures to ease their integration.

In April, he condemned Trump’s threat to destroy Iran as “truly unacceptable” and urged Americans to demand that US lawmakers “work for peace”.

Trump slammed the pontiff as “WEAK on Crime, and terrible for Foreign Policy” — to which Leo replied that he had a “moral duty to speak out”.

In an interview last month, Trump again criticised the pope, alleging that Leo believed it was “OK for Iran to have a nuclear weapon”.

“I think he’s endangering a lot of Catholics and a lot of people,” Trump said.

Asked about the comments, Leo said that the Catholic Church’s mission was to “preach peace” and the Gospel.

“If anyone wishes to criticise me for proclaiming the Gospel, let them do so truthfully,” he told reporters.