( Pope John Paul II was conscious but in "very grave" condition Friday after suffering heart failure during treatment for a urinary tract infection, his spokesman said, struggling with emotion.
Joaquin Navarro-Valls told reporters the pope, who was being treated at the Vatican, was "informed of the gravity of his situation" and decided to remain in his apartment overlooking St. Peter's Square.
John Paul, 84, participated in Mass and received some top aides Friday morning, Navarro-Valls said.
"The pope is still lucid, fully conscious and extraordinarily serene," Navarro-Valls said. He said the pope remained in "very grave" condition with unstable blood pressure.
John Paul asked aides to read him the biblical passage describing the final stage of the Way of the Cross, the path that Christ took to his crucifixion, Navarro-Valls said. In that stage, according to the Bible, Christ's body was taken down from the cross, wrapped in a linen shroud and placed in his tomb.
Navarro-Valls said the pope followed attentively and made the sign of the cross.
"This is surely an image I have never seen in these 26 years," Navarro-Valls said. Choking up, he walked out of the room.
The pope suffered heart failure and septic shock, during treatment for a urinary tract infection on Thursday, the Vatican said earlier Friday, but it denied an Italian news report that he was in a coma.
John Paul's health declined sharply Thursday, when he developed a high fever brought on by the infection.
Thousands of pilgrims gathered on St. Peter's Square to stand vigil for John Paul, many tearfully gazing up at his third-floor window, and people around the world joined in prayer.
The pope received the sacrament for the sick and dying on Thursday evening. Formerly called the last rites, the sacrament is often misunderstood as signaling imminent death. It is performed both for patients at the point of death and for those who are very sick -- and it may be repeated.
The Rome daily La Repubblica reported Friday that the sacrament was administered by John Paul's closest aide, Polish Archbishop Stanislaw Dziwisz, who serves as his private secretary. Dziwisz had given the pontiff the same sacrament on Feb. 24 just before the pope underwent a tracheotomy to insert a breathing tube in his throat at the Gemelli Polyclinic hospital, the newspaper said.
John Paul's 26-year papacy has been marked by its call to value the aged and to respect the sick, subjects the pope has turned to as he battles Parkinson's disease and crippling knee and hip ailments.
Italy's Apcom news agency reported Friday morning that the pontiff had fallen into a coma, but the Vatican dismissed the report.
On Friday, John Paul received several top aides, including the Vatican No. 2, Secretary of State Cardinal Angelo Sodano; undersecretary of state Archbishop Leonardo Sandri; the pope's vicar for Rome, Cardinal Camillo Ruini; his doctrinal chief, Cardinal Joseph Ratzinger; the Vatican foreign minister, Archbishop Giovanni Lajolo; and American Cardinal Edmund Szoka, the governor of Vatican City.
The pontiff was attended to in his apartment by the Vatican medical team, and provided with "all the appropriate therapeutic provisions and cardio-respiratory assistance," the Holy See said.
It said the pope was being helped by his personal doctor, two intensive care doctors, a cardiologist, an ear, nose and throat specialist and two nurses.
Heart failure occurs when the heart no longer has the strength to pump blood through the body, and is a sign that the body's cardiac system is failing.
Dr. Paolo Nardini, a Rome physician who is not part of the pope's team, said "a heart attack, which is very serious, affects only the heart, while heart failure signals a breakdown of the entire system, basically uncurable."
Dr. Peter Weissberg, medical director of the British Heart Foundation, said septic shock "puts a phenomenal strain on the heart."
In a statement released Friday, Weissberg said that "those already suffering from heart disease -- including those with heart failure -- are even more susceptible to septic shock. Infection triggers a profound loss of blood pressure, depriving organs around the body of their vital blood supply and putting an enormous strain on the heart."
Even the fittest patients need special care and medicine to survive, he said.
Ruini said he visited John Paul early Friday and found him "profoundly serene and fully lucid."
"I prayed with him for a moment which profoundly moved me. Certainly the pope has completely left himself in God's hands. I invite all Romans and Italians to intensify prayers for him in this moment," Ruini told private TG5 television.
He asked Italians to pray for John Paul, and said a special Mass for the pope would be held at 7 p.m. at the basilica of St. John Lateran in Rome. The patriarch of Venice, Cardinal Angelo Scola, also planned a Mass in St. Mark Basilica at the same time.
Around the world, people of different faiths joined in prayer for John Paul.
"Catholics, fellow Christians ... will be praying for him at this time as he comes toward the end of his extraordinary and wonderful life," said Cardinal Cormac Murphy-O'Connor, the archbishop of Westminster and one of the most senior Catholic clerics in Britain, speaking to reporters outside London's Westminster Cathedral.
In France, Muslim leader Dalil Boubakeur said Muslims were praying for the pope, describing him as a "man of peace" whose stature has been a determining factor for change in the world.
In the pope's home country, Poles flocked to churches as word spread of his deteriorating condition.
"I want him to hold on, but it is all in God's hands now," said 64-year-old Elzbieta Galuszko at the church where the pope was baptized in Wadowice, southern Poland. "We can only pray for him so he can pull through these difficult moments."
Hospitalized twice last month following two breathing crises, and fitted with a breathing tube and a feeding tube, John Paul has become a picture of suffering.
His 26-year papacy has been marked by its call to value the aged and to respect the sick, subjects the pope has turned to as he battles Parkinson's disease and crippling knee and hip ailments.
It is not clear who would be empowered to make medical decisions for an unconscious pope. The Vatican has officially declined to comment whether John Paul has left written instructions.