A drawn-looking Pope John Paul II (search), unable to preside over Palm Sunday (search) Mass for the first time in his 26-year papacy, appeared at his apartment window to greet tens of thousands of pilgrims who filled St. Peter's Square.

The crowd cheered as the pope appeared at the third-floor window, decorated with a braided palm frond and the crimson papal banner, and waved an olive branch to pilgrims who jammed the sun-drenched square for the ceremony ushering in Holy Week (search).

He appeared for no more than a minute and did not speak. He put his hand on his face and pounded the lectern once just before the white curtains at his window were drawn closed. Vatican television did not zoom in close on John Paul as it has in his past window appearances at the Vatican and earlier at the Rome hospital that treated him for a breathing crisis.

"With great joy I salute you," the pope said earlier in remarks read by an archbishop that included a special welcome for young people.

Cardinal Camillo Ruini, the pope's vicar for Rome, led the service in John Paul's place.

The Mass included a special prayer for the 84-year-old pontiff, calling him "our beloved father" and asking that he continue in his "service up to the gift of life."

"I came to see him," said Roswita Ginglas, a German pilgrim who, like many in the crowd, had tears in her eyes when the pope appeared. The crowd held up olive branches when John Paul came into view.

"You could feel his presence in the whole square, even if he didn't speak," said Pauline Everden, an Anglican tourist from England.

John Paul, who was discharged from the hospital last Sunday, has long presided over the ceremony marking the start of the most important week in the Roman Catholic liturgical year and which has been one of this pope's favorite appointments.

"It will be an unusual opening, that of Holy Week" without the pope at Palm Sunday Mass, Vatican Radio commented.

Potted olive trees surrounded the obelisk at the center of the square for the Mass, which commemorates Christ's triumphant entry into Jerusalem.

In his homily, Ruini spoke of Christ's ordeal and the "drama and mystery" of suffering and its meaning for humanity. The Italian cardinal said Christ's cross brings "new energies" and "shines with special clarity on the weary face of the Holy Father."

Andrea Glatz, an Austrian university student, said the pope "is like a magnet for young people, even though he's old and sick."

Many young people were in crowd for the Mass, part of the church's World Youth Day activities that culminates in mid-August with a celebration in Germany — the pope's only scheduled foreign trip this year.

John Paul mentioned World Youth Day in his message read by Archbishop Leonardo Sandri of Argentina, who has become the pope's public voice since his latest hospitalizations, but didn't say whether he would attend.

The pope is convalescing at the Vatican after Feb. 24 throat surgery to insert a tube in his windpipe and ease his second breathing crisis in less than a month.

John Paul has only spoken twice publicly — each time just a few sentences delivered in a raspy voice — since the operation. He also suffers from Parkinson's disease, which affects muscle control and makes it difficult for him to speak clearly.

Because of frail health, the pope already had scaled back some Holy Week traditions in recent years. For example, he would sit and pray while observing the Good Friday Colosseum procession, no longer carrying the cross.

But John Paul has heartened the faithful by bouncing back at times. Last year on Palm Sunday, he clutched a braided palm as a symbol of hope and peace and kissed babies held out to him during a drive around the square in his glass-paneled popemobile.

Sunday kicked off a busy week of events culminating in a week with Easter Sunday. The pope has designated other prelates to stand in for him, and the Vatican says his only commitment is his Easter blessing.