Ukrainian President Volodymyr Zelenskyy shared details from his first conversation with Pope Leo, describing it as "substantive" and "very warm."

Zelenskyy said he thanked the pope for his support of Ukraine.

"We deeply value his words about the need to achieve a just and lasting peace for our country and the release of prisoners," Zelenskyy tweeted on Monday. "We also discussed the thousands of Ukrainian children deported by Russia."

"I informed the Pope about the agreement between Ukraine and our partners that, starting today, a full and unconditional ceasefire for at least 30 days must begin. I also reaffirmed Ukraine’s readiness for further negotiations in any format, including direct talks -- a position we have repeatedly emphasized," Zelenskyy said. “Ukraine wants to end this war and is doing everything to achieve that. We now await similar steps from Russia."

Zelenskyy said he invited the pope to visit Ukraine and said they're planning an in-person meeting "in the near future."

Pope Leo XIV addressed thousands of journalists at the Vatican on Monday, warning against the "communication of all prejudice and resentment, fanaticism and even hatred."

"We do not need loud, forceful communication, but rather communication that is capable of listening and of gathering the voices of the weak who have no voice," the new leader of the Catholic Church said.

"Let us disarm words and we will help to disarm the world," he added. "Disarmed and disarming communication allows us to share a different view of the world and to act in a manner consistent with our human dignity."

"Blessed are the peacemakers," Leo said, recalling a blessing attributed to Jesus Christ.

The pope urged reporters "to strive for a different kind of communication, one that does not seek consensus at all costs, does not use aggressive words, does not follow the culture of competition and never separates the search for truth from the love with which we must humbly seek it."

"We must say 'no' to the war of words and images, we must reject the paradigm of war," Leo continued, also expressing the church's solidarity with imprisoned journalists.

Leo also again warned of the dangers associated with artificial intelligence, telling reporters that the technology has "immense potential" but "requires responsibility and discernment in order to ensure that it can be used for the good of all, so that it can benefit all of humanity."

"Thank you, dear friends, for your service to the truth," Leo said.

-ABC News Phoebe Natanson

Addressing crowds in St. Peter's Square on Sunday, Pope Leo XIV noted the 80th anniversary of the end of World War II and -- echoing his predecessor Pope Francis -- declared, "Never again war."

Leo urged an end to the ongoing wars in Ukraine and the Middle East. "I carry in my heart the suffering of the beloved Ukrainian people," he said. "Let us do everything possible to reach a genuine, just and lasting peace as soon as possible. May all prisoners be freed and children be able to return to their families."

"I am deeply saddened by what is happening in the Gaza Strip," he added. "Let the fire cease immediately. Let humanitarian aid be provided to the exhausted civilian population and let all hostages be freed."

"On the other hand, I welcomed with satisfaction the announcement of the ceasefire between India and Pakistan, and I hope that through the upcoming negotiations we can soon reach a lasting agreement," Leo continued.

-ABC News' Phoebe Natanson

Pope Leo XIV addressed crowds at the Vatican on Sunday, asking those gathered to pray for the priesthood.

The new pope spoke to the crowd to give the Regina Caeli prayer. Police estimated that there were around 100,000 people in St. Peter's Square to watch Leo's address.

-ABC News’ Phoebe Natanson