Donald Trump has issued a fresh verbal attack against Pope Leo XIV, accusing the pontiff of “endangering a lot of Catholics” because “he thinks it’s fine for Iran to have a nuclear weapon”.

The remarks come two days before Marco Rubio, the US secretary of state, meets Leo at the Vatican in an effort to ease the tensions sparked by Trump’s previous broadside against the Chicago-born pontiff over his condemnation of the US-Israeli war on Iran.

Speaking to Hugh Hewitt, a prominent conservative radio talkshow host on the US-based Salem News network, Trump said the pope “would rather talk about the fact that it’s OK for Iran to have a nuclear weapon, and I don’t think that’s very good”.

“I think he’s endangering a lot of Catholics and a lot of people,” the US president added. “But I guess if it’s up to the pope, he thinks it’s just fine for Iran to have a nuclear weapon.”

Leo has never said that Iran should have nuclear weapons, but has repeatedly opposed the war on the country and the subsequent escalation of the conflict in Lebanon and the wider Middle East, calling for ceasefires and dialogue.

Brian Burch, the US ambassador to the Holy See, said on Tuesday that he expected a “frank” meeting between Rubio, a Catholic, and Leo at the Apostolic Palace on Thursday morning.

“Nations have disagreements, and I think one of the ways that you work through those is … through fraternity and authentic dialogue,” Burch told reporters, adding that he thought Rubio was coming to the Vatican “in that spirit, to have a frank conversation about US policy, to engage in dialogue”.

Burch said he did not accept the idea that there was “some deep rift” between the US and the Vatican, saying that Rubio was coming so that each side could “better understand each other, and to work through, if there are differences, certainly to talk through that”.

The trip, which coincides with the first anniversary of Leo’s papacy, was organised after Trump lashed out at the pope in April, calling him weak and saying he was not doing a very good job as pontiff. Trump also shared an AI-generated image depicting himself as Christ, before deleting it and saying it had actually been a portrayal of him as a doctor.

Rubio will also endeavour to patch things up with the Italian government after Trump berated its prime minister, Giorgia Meloni, previously one of his closest allies in Europe, for calling out his remarks against Leo, rebuking her government for not supporting the strikes on Iran and threatening to withdraw US troops from Italy as a result.

Rubio will also meet the Vatican’s secretary of state, Pietro Parolin, before meeting Meloni and the Italian foreign minister, Antonio Tajani, on Friday morning.

The US vice-president, JD Vance – a Catholic convert – has also criticised the pope, saying the Vatican should “stick to matters of morality” and that Leo should be careful when it came to talking about theology and war.

Rubio and Vance attended the pope’s inauguration in May last year and had a private audience with him the day after, during which they handed him an invitation from Trump to the White House that Leo has not yet taken up.