VATICAN CITY -- Pope John Paul presided over his weekly general audience at the Vatican, appearing to be in relatively good form Wednesday morning.

Thousands of pilgrims packed Saint Peter's Square to pay tribute to the ailing pontiff during the 25th anniversary of his papacy.

The 83-year-old pope's voice was strong, although he had difficulty at times uttering his words. John Paul suffers from Parkinson's disease.

His stamina will be tested further with Thursday's anniversary mass, Sunday's beatification of Mother Teresa and a lengthy ceremony next week to install 30 new cardinals.

In recent months, the pope has been increasingly unable to complete his speeches. It's not clear what will happen if the pontiff becomes incapacitated. John Paul himself has often suggested he does not intend to resign, saying he'll carry out his mission to the end.