ROME, Italy — Ukrainian President Volodymyr Zelenskyy met Sunday with top U.S. officials and European leaders in Rome, ahead of a high-stakes phone call Monday between U.S. President Donald Trump and Russian President Vladimir Putin on ending the war in Ukraine.

The discussions came as Russia launched what Ukraine called its largest drone barrage against Ukraine since the start of its full-scale invasion in 2022, after the first direct talks in years between Moscow and Kyiv failed to yield a ceasefire Friday.

Zelenskyy spoke with U.S. Vice President JD Vance and Secretary of State Marco Rubio at the U.S. ambassador’s residence, after attending the inaugural Mass for Pope Leo XIV in St. Peter’s Square.

Zelenskyy said on social media that he had underscored the need for “real diplomacy” and reaffirmed Ukraine’s commitment to a “full and unconditional ceasefire.”

He said they discussed sanctions against Russia, bilateral trade, defense cooperation and plans for the upcoming prisoner exchange with Russia that was agreed in talks between the two sides in Istanbul.

Trump has said he plans to speak with Putin about stopping the “bloodbath” in Ukraine and then speak to Zelenskyy and leaders of various NATO countries.

The morning also marked the new pope’s first steps into a global role.

Pope Leo XIV celebrated an outdoor Mass formally inaugurating him as the 267th pope of the Roman Catholic Church, telling world leaders, the assembled hierarchy of his church and more than 100,000 faithful gathered in St. Peter’s Square that the church needs a new unity that recognizes its diversity.

Leo — who said Ukraine “awaits negotiations for a fair and lasting peace,” called for peace in Myanmar and urged the world not to forget those “reduced to hunger” — met privately with Zelenskyy after Mass.

Vance, who took part in Trump’s contentious meeting in the White House this year with Zelenskyy, shook hands briefly with the Ukrainian leader before Mass.

After Mass, Vance, whom the White House called “the first Catholic convert” to serve in the position, briefly shook the pope’s hand in a long receiving line of dignitaries and royals.

It was unclear whether he would get a private audience before returning to the United States on Monday.

“The authority and voice of the Holy See can play an important role in bringing this war to an end,” the Ukrainian president wrote on social media.

He thanked the Vatican for its readiness to become a platform for direct negotiations between Ukraine and Russia.

On Saturday, Rubio said the Vatican could be a venue for peace talks, taking up the Holy See’s longstanding offer after Leo vowed to personally make “every effort” to help end the war.

Ahead of a meeting in Rome with Vance and Italian Premier Giorgia Meloni, EU Commission President Ursula Von der Leyen urged parties to “push things forward.”

Meloni hosted a key trilateral meeting Sunday in Rome, bringing Vance and von der Leyen to the same table.

It was a diplomatic score for Meloni, who has been touted as a potential bridge-builder with the Trump administration, but so far had been unable to provide decisive breakthroughs amid increasingly strained relations with her main European partners.

“I hope that today can be a first meeting and a new beginning,” Meloni said, and Rome’s role is linked to “the need and the desire to promote dialogue.”

Addressing the Ukrainian conflict, Von der Leyen said that “what unites us on Ukraine is the pursuit of a just and lasting peace,” and thanked the U.S. for its strong commitment in trying to stop the war.

German Chancellor Friedrich Merz said he spoke to Zelenskyy and Rubio on the sidelines of the pope’s inauguration. Merz said he had agreed with the leaders of France and Britain “that we will speak again with the American president in preparation for this conversation.”

Merz told reporters that “my firm impression is that both the Europeans and the Americans are determined to work together, but now also in a goal-oriented manner, to ensure that this terrible war ends soon.”

Putin spurned Zelenskyy’s offer to meet face-to-face in Turkey after he proposed direct negotiations — although not at the presidential level — as an alternative to a 30-day ceasefire urged by Ukraine and its Western allies, including the U.S.

The talks in Istanbul broke up after less than two hours, although both sides agreed on exchanging 1,000 prisoners of war each, according to the heads of both delegations.

Also on Sunday, Russia fired 273 exploding drones and decoys targeting Ukraine’s Kyiv, Dnipropetrovsk and Donetsk regions, Ukraine’s air force said. Of those, 88 were intercepted and 128 lost, likely being electronically jammed.

Yuriy Ihnat, head of the air force’s communications department, told The Associated Press the barrage was the biggest drone attack since the start of Russia’s invasion.

Kyiv regional Gov. Mykola Kalashnyk said a 28-year-old woman was killed in a drone attack and three people, including a 4-year-old child, were wounded.

Russia’s Defense Ministry said its air defenses shot down seven Ukrainian drones overnight and 18 drones Sunday morning.

The New York Times contributed.