Messages of goodwill have been sent from all over the world for Pope John Paul II, who is gravely ill with heart and breathing problems.
Concern is writ large on the face of a Filipino woman
US President George W Bush and his wife Laura had joined those around the globe praying for him, the White House said.
Even China has wished the Pope a speedy recovery - the Communist state's first public message to a head of the Catholic Church since the 1950s.
Rome is braced for a huge influx of pilgrims as the Pope's health worsens.
Catholics in Asia and South America are flocking to churches for special prayer meetings for the ailing pontiff.
In the Brazilian city of Sao Paulo, some 20,000 people gathered to pray for the Pope.
"We know how much he loves Brazil and also how much we Brazilians love the Pope," the city's archbishop, Cardinal Claudio Hummes, told the congregation.
The Pope's plight has provoked concern among Catholics throughout the region.
A Mexican woman was quoted by Spanish television saying she had come with her daughter the city of Guadalupe to pray for his recovery.
Vigils were being held in Bethlehem, which Christians believe was the birthplace of Jesus Christ.
Churches in the Philippines glowed with the light of many candles.
In the Pope's native Poland, the archbishop of Krakow told Poles not to be ashamed of showing their emotions.
Many young people were among those offering prayers.
"He can't leave us when times are so difficult, when there is so much evil - terrorism, unemployment, no more hope," a student told the AFP news agency.
'Prepared for the worst'
White House spokesman Scott McClellan said officials were in close contact with the Vatican about the Pope's health.
"The president and Mrs Bush join people all around the world who are praying for the Holy Father," he said.
"The outpouring of love and concern from so many, including millions of Americans, is a testimony to his greatness. During this time, His Holiness is in the thoughts and prayers of us all."
US Secretary of State Condoleezza Rice, meanwhile, paid tribute to the "tremendous contribution" made by the Pope to the collapse of communism in Eastern Europe in 1989-91.
He had continued to be a voice for people seeking freedom, she said.
In China, which suspended ties with the Vatican in 1951, a foreign ministry spokesman said he hoped the Pope would recover soon.
Beijing insists that its Catholics only pray in state-approved churches that do not recognise the Pope's authority.
Many Chinese Catholics do however continue to run the risk of arrest by honouring the Pope in clandestine ceremonies.
The faithful have also packed churches in the Philippines, where the Pope's last visit drew millions onto the streets.
"We are praying for his health in these days of illness. But we are prepared for the worst," Rey Caluba, a parish priest in a Manila church, said.
In Sydney, Bishop Julian Porteous praised the pontiff as "one of the great men of our time".