Pope Francis condemned "armed conquest, expansionism, and imperialism" on Thursday and called Putin's invasion of Ukraine a "cruel and senseless war of aggression." 

"Reconciliation among separated Christians, as a means of contributing to peace between peoples in conflict, is a most timely consideration these days, as our world is disrupted by a cruel and senseless war of aggression in which many, many Christians are fighting one another," the Pope told a delegation of Orthodox leaders. 

Earlier in the week, the Pope decried a "barbarous" missile strike on a Ukrainian mall that left 18 dead, saying that he carries "dear and martyred Ukraine" in his heart every day. 

Pope Francis speaking during Mass

Pope Francis holds his homily during  a Mass on  the Solemnity of the Epiphany at St. Peter's Basilica on Jan. 6, 2022, in Vatican City, Vatican.  (AleVatican Pool/Getty Images)

The Pope's comments this week mark a more forceful condemnation of Russia's actions since Putin invaded Ukraine on Feb. 24. 

He had raised eyebrows around the world last month when he suggested to the Italian Corriere della Sera newspaper that the "barking of NATO at Russia's door" may have forced Russia to invade. 

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Then in an interview published on June 18, the Pope said that the war was "perhaps somehow either provoked or not prevented."

"Someone can tell me at this point: but you are in favor of Putin! No, they are not," he told Jesuit magazine La Civiltà Cattolica. "It would be simplistic and wrong to say such a thing. I am simply against reducing complexity to the distinction between good and bad, without thinking about roots and interests, which are very complex."

The Vatican has sought to maintain relations with Patriarch Kirill, the head of the Russian Orthodox Church and a key ally of Putin. 

Pope Francis and Kirill

The head of the Russian Orthodox Church Patriarch Kirill, left, and Pope Francis talk during a meeting at the Jose Marti airport in Havana, Cuba, in February 2016. (Adalberto Roque/Pool photo via AP)

Pope Francis and Kirill met in Cuba in 2016, marking the first time that a pontiff and leader of the Russian Orthodox Church have met in person since the Great Schism in 1054. 

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The two were supposed to meet in Jerusalem earlier this month, but the Vatican called the trip off in April. 

Pope Francis said in May that Kirill must be careful not to "transform himself into Putin's altar boy," sparking criticism from the Russian Orthodox Church

Reuters contributed to this report.