Pietro Parolin, a 70-year-old Italian polyglot who entered the seminary at just 14, is currently pitted as favourite to replace Francis as the pope is still in hospital.

Around 4,000 people gathered in St. Peter's Square to pray for Pope Francis, who is critically ill with pneumonia. Despite slight improvements in his health, concerns grow over his fragile condition.

The Vatican press office said Cardinal Parolin will lead a rosary for the pontiff in St. Peter's Square at 9 p.m. local time. The U.S. bishops urged Catholics to join that prayer at the same time, 3 p.m. on the East Coast.

The Vatican has detailed laws and rituals to ensure the transfer of power when a pope dies or resigns, but not when he is sick