Pope John Paul II's poor health has deteriorated further, the Vatican has said, as Catholics around the world prepare for his approaching death.
The Pope asked not to return to hospital for treatment
No word has been heard for more than 12 hours on his condition, but a briefing has been scheduled for 0930GMT.
At the last update, his breathing was reportedly shallow, his blood pressure low and there were problems with both his heart and kidneys.
Thousands of people held an evening vigil in St Peter's Square.
Up to 70,000 attended past midnight, but numbers had dwindled to just a few hundred by the early hours.
"Stay with us. Don't leave us," the crowds chanted, many crying uncontrollably.
The Vatican made three statements on Friday, seemingly to prepare Catholics to expect the worst.
Unusually, it kept its press centre open all Friday night, but closed it at 0600 (0400 GMT) on Saturday, saying it would reopen at 0900.
Cardinals - who will elect a new pope after John Paul dies - are arriving in Rome from all over the world, the Italian media have reported.
The Pope's vicar general of Rome said the pontiff was already "at one" with Jesus Christ.
He "already sees and touches the Lord," Cardinal Camillo Ruini told a packed Mass in Rome's St John Lateran cathedral.
"I invite all Romans and all Italians to intensify their prayers for him," he said.
"We want to be close to him in this hour through the same loving closeness with which John Paul II has accompanied us for nearly 27 years."
Another senior clergyman, Angelo Comastri, told about 30,000 people gathered in St Peter's Square: "This evening or this night, Christ opens the door to the Pope."
Vatican spokesman Joaquin Navarro-Valls said on Friday evening that the Pope's overall condition had been "notably compromised".
But he added that the Pope was visibly participating in prayers around his sickbed.
The Pope's condition deteriorated on Thursday after he developed a urinary tract infection that later brought on "septic shock and a cardio-circulatory collapse".
He was given the Catholic sacrament for the sick and dying - called the Anointing of the Sick.
But the Pope decided not to return to Rome's Gemelli hospital.
He was being treated in his apartment by a team of four top consultants and his private doctor Renato Buzzonetti.
Catholics around the world have been praying for the Pope.
In the Pope's homeland, Poland, churches have been packed with worshippers throughout the day.
The Archbishop of Krakow, Franciszek Macharski - a long-time friend of the Pope - told his audience: "Do not feel shame at showing your emotion and at shedding tears."
US President George W Bush and his wife Laura had joined those around the world who were praying for him, White House spokesman Scott McClellan said.