AMNA NAWAZ: Secretary of State Marco Rubio today tried to smooth over another conflict sparked by the Iran war, this one with the pope.

A meeting between Rubio and Pope Leo came after President Trump repeatedly accused the pontiff of wanting Iran to have a nuclear weapon and of being -- quote -- "weak on crime."

The pope has responded in turn.

Stephanie Sy reports.

STEPHANIE SY: Today, the U.S.

dispatched its chief diplomat on a unique mission, to the Vatican... POPE LEO XIV, Leader of Catholic Church (through translator): Mr.

Secretary.

MARCO RUBIO, U.S.

Secretary of State: It's great to see you.

STEPHANIE SY: ... holding a meeting with the pontiff himself in a bid to ease tensions between Washington and the Holy See amid President Trump's repeated attacks against Pope Leo, chiefly on the Iran war.

They exchanged pleasantries, as well as gifts, in the pope's private library.

MARCO RUBIO: It has the seal of the State Department.

STEPHANIE SY: But the meeting was not all breaking bread.

Rubio, a practicing Catholic and the pope, sat down to discuss, as the Vatican put it, "countries affected by war, political tensions and difficult humanitarian conditions, as well as on the need to work tirelessly in favor of peace."

The direct dialogue follows President Trump's war of words with the pope on the Iran conflict and other issues, like immigration, outside the Oval Office last month.

DONALD TRUMP, President of the United States: You cannot have a nuclear Iran.

Pope Leo would not be happy with the end result.

You would have hundreds of millions of people dead, and it's not going to happen -- So I can't -- I think he's very weak on crime.

STEPHANIE SY: And earlier this week.

DONALD TRUMP: 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.

But I guess, if it's up to the pope, he thinks it's just fine for Iran to have a nuclear weapon.

STEPHANIE SY: But Pope Leo on Tuesday denied that accusation.

POPE LEO XIV (through translator): If anyone wishes to criticize me for proclaiming the Gospel, let them do so with truth.

The church has for years spoken out against all nuclear weapons, so there is no doubt about that.

And so I simply hope to be heard for the sake of the word of God.

STEPHANIE SY: The pope has also continued to call out Trump's policy of mass deportations, citing the New Testament in his repeated criticisms.

POPE LEO XIV: I have no fear of either the Trump administration nor speaking out loudly about the message of the Gospel.

And that's what I believe I am called to do, what the church is called to do.

STEPHANIE SY: Rubio's visit aside, that calling continues to put the Vatican at odds with Washington, even as support for President Trump among America's 53 million Catholics is on the decline.

For the "PBS News Hour," I'm Stephanie Sy.

AMNA NAWAZ: For more, I'm joined now by Miguel Diaz.

He's former ambassador to the Vatican under the Obama administration and a theology professor at Loyola University Chicago.

Ambassador Diaz, thank you so much for joining us.

I will begin by asking you what you took away from today's meeting.

Do you think Secretary Rubio smoothed over relations with Pope Leo?

MIGUEL DIAZ, Former U.S.

Ambassador to the Vatican: First of all, thank you for -- it's such an honor to be here and to be able to speak with you.

So, the secretary went to the Vatican to speak to the Holy Father, who is both the head of a sovereign entity and also the head of the 1.4 billion Catholics.

Throughout our history of diplomatic relations with the Holy See, we, the United States, has related to the Holy See as a sovereign entity, as a global humanitarian actor and as a moral voice that has consistently defended the dignity of all human persons.

This post, we call it a great listening post, because it has eyes and ears everywhere.

And so it is an incredibly productive and valuable post, not only in times of peace, but clearly in times of war.

And so, when the secretary of state stepped into the Vatican today, I hope that there -- was in the spirit of what the church has since Pope Francis called synodality, that there has been an authentic listening to the kind of wisdom that emerges in any effort, any authentic effort to build bridges.

And so we won't know until -- actions speak louder than words.

We won't know until some weeks evolve here whether the secretary will be able to bring back some good news in terms of the human family in those conversations.

But we remain hopeful.

Diplomacy always should be given the last -- the first and the last word in that violence.

AMNA NAWAZ: Can I just ask you what you make of this moment?

I mean, the fact that Vatican officials said the U.S.

had requested this meeting, there was a clear intention there by the secretary to go and try to reduce some of the tensions we have seen.

But then you saw President Trump just this week accusing Pope Leo of endangering a lot of Catholics by opposing the war.

What do you make of the fact that we are where we are right now?

MIGUEL DIAZ: Yes, I think - - I do think it's not wise and certainly not diplomatically wise to call the pope that he's terrible on foreign policy.

And, as your earlier report, the pope has already said that, if you're going to -- in terms of the pope favoring nuclear weapon, well, that has not been the case.

It's been the tradition of popes, of people teaching to oppose, in fact, nuclear weapons.

And so this is in many ways unpresidential and is unprecedented in the sense that you would call out a pope like this, especially when it is something that is benefiting the common good.

And we are talking about someone who recognizes that there is tremendous polarization in the world, polarization within our own nation.

But there's tremendous polarization in the world and, in the words of Pope Francis, who said there's this horrific globalization of indifference.

And that needs to be countered by not violence, but by peace.

And so I think this is where you see this first American pope, a pope from the United States, saying, enough.

Enough to the idolatry of the self and money, enough to the abuse of power, and enough really to war and violence as the means or the ends to resolving conflict.

AMNA NAWAZ: We have a minute or so left, but I have to ask you, because the Vatican says in their statement that they did discuss the need for peace in that meeting.

Do you believe that this pope, Pope Leo, can influence U.S.

foreign policy in any way?

MIGUEL DIAZ: Well, the pope has called for unarmed and a disarming peace.

I -- we look at the two -- the statements from the State Department and the Vatican, and it's interesting.

Yes, there -- the two statements are very similar in terms of affirming the bilateral nature and the importance of that.

They both affirm peace and they both affirm human dignity.

But it's interesting that the statement from the Vatican goes a little bit more in detail, because I quote here.

It says "with particular attention to countries affected by war, political tensions and difficult humanitarian situations."

So it is a concretization of issues that affect the issues that affect human dignity.

As to whether or not the pope can bring about some impact in terms of our foreign policy, that remains to be seen.

But, again, we hope that the better angels have prevailed today at the Vatican and that Secretary Rubio can come back to the White House and have an honest conversation with our president and acknowledge that the way forward, it's not violence, but bridge-building.

AMNA NAWAZ: That is Miguel Diaz, former U.S.

ambassador to the Holy See, joining us tonight.

Mr.

Ambassador, thank you so much for your time.

MIGUEL DIAZ: Thank you so much.