ROME, Italy (AP) — Ukrainian President Volodymyr Zelenskyy met with top U.S. officials and European leaders on Sunday 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 between Moscow and Kyiv in years 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 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.

Zelenskyy also met with the new pope after the Mass. “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.

Rubio on Saturday 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 Italy’s Premier Giorgia Meloni, EU Commission head Ursula Von der Leyen urged parties to “push things forward."

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 himself 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. Ukraine’s intelligence chief, Kyrylo Budanov, said on Ukrainian television Saturday that the exchange could happen as early as next week.

Russia on Sunday fired a total of 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 full-scale invasion.

Previously, Russia’s largest known single drone attack was on the eve of the war’s third anniversary, when Russia pounded Ukraine with 267 drones.

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

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

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Morton reported from London. Associated Press writers Yehor Konovalov and Volodymyr Yurchuk in Kyiv, Ukraine, contributed.

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Follow AP’s coverage of the war in Ukraine at https://apnews.com/hub/russia-ukraine