By David Willey
BBC News, Rome
Pope Benedict is sending his foreign minister to Moscow for a working visit to sound out the possibilities of exchanging ambassadors with Russia.
Benedict XVI is promoting unity among Christians of different faiths
Archbishop Giovanni Lajolo, the Pope's foreign minister, has been invited by his Russian counterpart, Sergei Lavrov.
Relations between the Vatican and Russia have long been at a low ebb.
Low-level diplomatic contacts were restored after an historic visit to the Vatican by former Soviet Union President Mikhail Gorbachev in 1989.
Pope Benedict has made the promotion of Christian unity one of the main goals of his pontificate.
The head of the Russian Orthodox Church, Patriarch Alexy II, accused the late Pope of poaching converts by establishing Catholic dioceses inside traditionally Orthodox territories in Russia.
With the election of the new Pope earlier this year, both sides now seem more amenable to dialogue.
During his visit to Moscow, Archbishop Lajolo will meet members of the Russian parliament as well as his counterpart in the Russian Orthodox Church, Metropolitan Kirill.
Meanwhile a top Vatican cardinal, talking to correspondents in Rome, confirmed the ice is thawing between the Catholic and Orthodox churches.
Cardinal Walter Kasper, who is in charge of the Vatican's relations with other Christian churches - both Protestant and Orthodox - ruled out a visit to Moscow the very near future by Pope Benedict.
But theological dialogue between the two churches is about to resume, he said, after a break of four years, with a meeting in Rome in December.