Pope John Paul made a surprise appearance at his hospital window in Rome today (Sunday), blessing people gathered outside the clinic where he was taken last week for emergency treatment of renewed breathing problems.

The pope appeared (at a 10th-floor window of the Gemelli Hospital) and waved to the crowd moments after the weekly Angelus prayer service in St. Peter's Square, but he did not speak.

The number-two official at the Vatican, Cardinal Angelo Sodano, stood behind the seated pope, who wore his customary white vestments. The pontiff blessed the crowd by making the sign of the cross in clear gestures.

At the Vatican, an archbishop appeared in place of John Paul to bless pilgrims, and he read a message from the pope thanking Catholics for their affection and asking for their prayers. The crowds (outside St. Peter's Basilica) were unaware of the pope's brief appearance at the hospital.

The 84-year-old pope, leader of the world's Roman Catholics since 1978, has never before failed to participate in the Sunday service at St. Peter's -- either in person or through a live or recorded message from another location during his travels. However, doctors who installed a breathing tube in his throat on Thursday have said he should not speak for the time being, so he can recover from his recent breathing difficulties.

He has been communicating with aides in writing.