The head of Russia's influential Orthodox Church, Patriarch Kirill, told an envoy of Pope Francis on Thursday their churches should work together to avert "negative political developments and serve the cause of peace and justice."
Kirill is a strong supporter of President Vladimir Putin's decision to send troops into Ukraine, while Francis has called repeatedly for an end to the conflict, which has destroyed Ukrainian villages and towns, caused the deaths of tens of thousands of people and driven millions more from their homes.
"I think that today... the churches can through their joint efforts avert the negative development of political events and serve the cause of peace and justice," Kirill told the envoy, Cardinal Matteo Zuppi.
"It is very important that in this difficult time Christian communities in the East and the West take part in this process of reconciliation," the patriarch added.
Zuppi, who was on the second day of his trip to Moscow, stressed that Pope Francis was very keen to hear directly Kirill's views on the Ukraine situation.
Earlier, Zuppi discussed humanitarian issues related to the conflict in Ukraine and the protection of human rights with Russia's Children's Commissioner Maria Lvova-Belova.
The International Criminal Court (ICC) in March issued an arrest warrant for both Lvova-Belova and for President Vladimir Putin, accusing them of the war crime of illegally deporting hundreds of children from Ukraine.
Moscow said the warrants were legally void as Russia was not a member of the ICC. It also denies accusations of human rights abuses in Ukraine.
Russia has not concealed a programme under which it has brought thousands of Ukrainian children to Russia, but presents it as a humanitarian campaign to protect orphans and children abandoned in the war zone.
Zuppi held talks on Wednesday with one of Putin's advisers, Yuri Ushakov, which the Vatican said had gone well.
Putin's spokesman Dmitry Peskov said on Thursday the Kremlin "highly appreciates the efforts and initiatives of the Vatican to find a peaceful solution to the Ukrainian crisis".