AA RCH BISHOP Agostino Casaroli, a shrewd diplomat with a reputation for troubleshooting among the communists, left Rome for Moscow on Wednesday, making the first official visit to the Soviet Union by a high-ranking Catholic prelate.
Mgr. Casaroli's journey was for the purpose of depositing the document by which the Holy See will adhere to the nuclear non proliferation treaty. But the Vatican said that the Archbishop would also meet Soviet officials to discuss Church-State and East-West problems, and the possibility of greater freedom for Catholics in the U.S.S.R.
Mgr. Casaroli is responsible for the Vatican's relations with non-Catholic countries, and is credited with diplomatic agreements with Hungary since 1964, and those made between the Vatican and Yugoslavia last August.
He will be accompanied to Moscow by Mgr. Achille Silvestrini, from his own office, and Professor John Nemo, from the University College of Cape Coast in Ghana, representing the Council of Catholic Laymen.
Observers in Moscow noted that Mgr. Caseroli's visit to Moscow was not strictly necessary since the Vatican will support the treaty in similar ceremonies in London and Washington where there are Vatican envoys.