The highest ranking Vatican official to visit Russia since the start of Pope Benedict's papacy began a mission to Moscow on Monday to test the waters for improving ties with the Russian Orthodox Church.
In an unexpected announcement, the Vatican said Cardinal Walter Kasper, head of the Pontifical Council for Promoting Christian Unity and Benedict's point man for relations with other Christians, would spend four days in Moscow.
The statement said Kasper, a German like Pope Benedict, had gone to "continue the dialogue with the Russian Orthodox Patriarchate" begun when the new Pope was inaugurated.
Kasper's departure for talks in Moscow was the latest salvo in Benedict's offensive to improve relations with other religions since his election to the papacy on April 19.
A Vatican official said the purpose of Kasper's trip was to get a first-hand feeling of the atmosphere in Moscow.
The Russian Orthodox Church, which split from Rome in the Great Schism of 1054, maintained chilly relations with the late Pope John Paul, a Pole who had campaigned against the Soviet Union and sought in vain to visit post-communist Russia.
"Kasper's mission is to do a little digging and keep his ears open in order to see if the obstacles that existed under the previous papacy can be overcome," the official, a prelate, said.
The source said it was still not clear if Kasper would meet Patriarch Alexiy II, the head of the Russian Orthodox Church, whose personal relations with John Paul were often scratchy.
Since the break up of the former Soviet Union in 1991, the Russian Orthodox Church has accused Catholics of using new-found freedoms to woo converts away from the Orthodox Church.
The Vatican has rejected accusations of so-called "soul poaching" as unfounded.
Worldwide orthodoxy, which is organised under national churches, has a total of some 220 million members, as opposed to some 1.1 billion Roman Catholics.
John Paul had standing invitations from a string of Russian presidents to visit Moscow but Alexiy always vetoed the idea.
Alexiy told the Kommersant daily newspaper last month he believed Benedict had the personal qualities to improve relations with the Orthodox Church.