VATICAN CITY- U.S. Secretary of State Marco Rubio expects a "frank" meeting with Pope Leo during a visit to the Vatican on Thursday, the U.S. ambassador said, after President Donald Trump took a fresh pot-shot at the pope for criticizing the U.S.-Israeli war in Iran.

"Nations have disagreements, and I think one of the ways that you work through those is ... through fraternity and authentic dialogue," Brian Burch, the U.S. ambassador to the Holy See, said on Tuesday.

"I think the Secretary is coming here in that spirit," Burch told journalists. "To have a frank conversation about U.S. policy, to engage in dialogue."

Trump has repeatedly disparaged the first U.S.-born pope in recent weeks, drawing a backlash from Christian leaders across the political spectrum.

In his latest comments, Trump told right-wing radio talk show host Hugh Hewitt that "the Pope would rather talk about the fact that it's okay 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. But I guess if it's up to the Pope, he thinks it's just fine for Iran to have a nuclear weapon," Trump said.

Leo has never said Iran should have nuclear weapons, but has opposed the war which Trump says is aimed at ending Iran's nuclear program.

Cardinal Pietro Parolin, the Vatican's top diplomat, said he did not know if Leo would respond to Trump's latest comments.

"The pope will go ahead on his path, in the sense of preaching the Gospel (and) peace," Parolin, the Vatican's Secretary of State, told journalists. He said Leo would speak about peace at every opportunity, "convenient and inconvenient".

RUBIO WILL 'TALK THROUGH' DIFFERENCES WITH POPE

Rubio is Catholic, as is Vice President JD Vance. The two met Leo a year ago after attending his inaugural mass, the Trump administration's only previous known cabinet-level meetings with the pope.

Burch was asked after an event hosted by his embassy at Rome's Gregorian University on Tuesday if Rubio was hoping to repair Trump's relationship with Leo.

"I don't accept the idea that somehow there's some deep rift," the ambassador responded. Rubio is coming, Burch said, so that the U.S. and the Vatican can "better understand each other, and to work through, if there are differences, certainly to talk through that".

Rubio is also set to meet on Friday with Italian Prime Minister Giorgia Meloni, who defended the Pope. Her defence minister has said the war in Iran puts U.S. leadership at risk.

Leo, who marks his first year as leader of the 1.4-billion-member Catholic Church on Friday, maintained a relatively low profile on the global stage in the first months of his papacy but has emerged in recent weeks as a firm critic of the war on Iran.

The pope has also sharply criticized the Trump administration's hardline anti-immigration policies. And he has called for dialogue between the U.S. and Catholic-majority Cuba, which has suffered frequent blackouts owing to U.S. sanctions intended to put pressure on its one-party Communist government.

(Reporting by Joshua McElweeEditing by Cristina Carlevaro, Peter Graff and Kevin Liffey)