Pope Francis in an interview published on Tuesday slammed NATO over the Ukraine war.
Questioning the conflict's causes, the pope spoke of an "anger" in the Kremlin which could have been "facilitated" by "the barking of NATO at Russia's door".
The remarks came as the pope reiterated that he requested a meeting with Russian president Vladimir Putin over Ukraine, while comparing the scale of the bloodshed in the country to the genocide in Rwanda.
The pontiff told Italy's Corriere Della Sera newspaper that he had sent a message to Putin around 20 days into the conflict saying that "I was willing to go to Moscow".
"We have not yet received a response and we are still insisting, though I fear that Putin cannot, and does not, want to have this meeting at this time," Francis said.
"But how is it possible to not stop such brutality? Twenty-five years ago, we lived through the same thing with Rwanda," he said.
About 800,000 people were killed between April and July 1994 as the extremist Hutu regime tried to wipe out Rwanda's Tutsi minority, in one of the 20th century's biggest massacres.
The pope has repeatedly called for peace in Ukraine and denounced a "cruel and senseless war" without mentioning Putin or Moscow by name.
"I'm not going to Kyiv for now. I feel I shouldn't go. I have to go to Moscow first, I have to meet Putin first," he said.
Francis also said Russian Orthodox Patriarch Kirill, a close Putin ally, "cannot become Putin's altar boy".
Dialogue with the Orthodox Church, which separated from the Catholic Church in 1054, is a priority of Francis's pontificate.
But since Russia invaded Ukraine on 24 February, the pope's calls for peace have contrasted with Kirill's defence of Putin's fight against Russia's "external and internal enemies".
Meanwhile, the Pope's remark on NATO sparked a reaction in Poland where education minister Przemyslaw Czarnek said on public television: "For sure, many of us are taking our heads in our hands-on hearing what the pope has said."
Poland which shares a border with both Russia and Ukraine is a member of the US-led military alliance.
With inputs from AFP