On Monday, a EU diplomat said that Russia has concentrated more than 150,000 troops on Ukraine's border and in annexed Crimea.
The pope spoke of the escalating situation on Sunday, after praying the midday Regina Caeli with pilgrims in St. Peter's Square.
The Holy Father's appeal was urgent, as he asked, "Please, I firmly hope that the increase of tensions may be avoided ..."
He led a Hail Mary for peace. Here is what he said: