On Wednesday a Florida judge ordered the tube delivering food and water to Schiavo kept in place another 48 hours.
Pinellas County Circuit Judge George Greer said he needed time to consider legal challenges raised by the woman's parents, including the possibility that her husband, Michael Schiavo, was unfit to act as her guardian.
In statements on Vatican Radio, Cardinal Renato Martino, president of the Pontifical Council for Justice and Peace, said: "If Mr. Schiavo succeeds legally in causing the death of his wife, this not only would be tragic in itself, but would be a grave step toward the legal approval of euthanasia in the United States."
He added: "I would like to remind everyone in this connection, about all that the Holy Father has said in past days to the Pontifical Academy for Life, confirming that the quality of life is not interpreted as economic success, beauty and physical pleasure, but consists in the supreme dignity of the creature made in the image and likeness of God.
"No one can be the arbiter of life except God himself."