For the first time ever, a pope will meet with a patriarch of the Russian Orthodox Church, the Vatican has announced.
The meeting is aimed at improving ties between the Roman Catholic Church and the Orthodox Church, which broke away in the year 1054.
"The importance of this event is this is the first time the pope meets the patriarch — it is extremely important for ecumenism," Father Federico Lombardi, the Vatican spokesman, said at a news conference Friday.
The Orthodox Church split away nearly 1,000 years ago amid disagreements over liturgy and power-sharing. Over the centuries, the relationship has been full of rancor and distrust.
The Vatican and the wider Orthodox Church's spiritual leadership have moved to patch things up over the last century, and Francis has met its current spiritual head, Patriarch Bartholomew. But the relationship has remained troubled because the powerful Russian branch, whose 150 million members account for two-thirds of all Orthodox Christians, has kept its distance.
Lombardi said the historic meeting this month follows two years of diplomacy. "This is not improvised," he said.
The meeting will take place in the airport in Havana, a location that suits the longtime desire of both churches to meet on neutral ground as well as the schedules of Kirill and Francis. The Russian patriarch will be in Cuba as part of a tour of Latin America, while Francis will stop at the airport on his way to Mexico.
Cuba also has significance because it was for many years an ideological front line between Catholicism and Russian communism, while in 2014, Francis helped reopen diplomatic relations between Cuba and the U.S.
The two leaders will meet for nearly two hours before signing a joint declaration at an event hosted by Cuban leader Raul Castro.
The signing, Lombardi said, will signify "a dialogue that can overcome previous obstacles."
Metropolitan Illarion, foreign policy chief of the Russian Orthodox Church, said Friday there were still basic disagreements to resolve, including the role of Orthodox churches in western Ukraine.
The killings of Catholics and Orthodox Christians in Middle East conflicts were a key motive for scheduling the meeting, he said.
"The situation in the Middle East, in northern and central Africa and in other regions where extremists are perpetrating a genocide of Christians requires immediate action and an even closer cooperation between Christian churches," Illarion said.
"In this tragic situation, we need to put aside internal disagreements and pool efforts to save Christianity in the regions where it is subject to most severe persecution."
The rift between the churches goes far beyond a battle for converts in Russia. One Vatican expert said it is largely about who would come out on top if they ever reunited. There are 1.2 billion Catholics.
"It's about who has the bigger hat," said Robert Mickens, editor in chief of Global Pulse. "The Russians are afraid of being swallowed up."
Mickens said the Vatican has traditionally viewed itself as superior to the Russian Orthodox Church. But Francis has made friends in Moscow by behaving more like an equal.
Mickens added that the Russians had decided to act while Francis was still in office. "They fear a conservative backlash in Rome after Francis," he said.
A key turn in church relations came in November 2014, when Francis bowed to Bartholomew during their meeting in Istanbul, Turkey, said Gerard O'Connell of the news organization Vatican Insider. The rapprochement "has a lot to do with the humility shown by Francis to the Orthodox Church," he said.
Kington is a special correspondent.