Pope John Paul has called on Catholics to show more discipline in order to help Rome advance towards unity with Protestants.
He made his remarks before completing the final day of his visit to the Swiss capital Bern, which was his first journey outside Italy in almost nine months.
The remark is seen as a rebuke to prominent Catholics who said the Pope should resign because concern for his health was distracting from the message he was preaching.
Protestant churches turned down an invitation to today's Papal Mass outside Bern in protest at the Vatican's ban on inter-communion, which Swiss Protestants have been encouraging for decades.
The 70,000-strong congregation that did attend gave the Pope a warm welcome.
And despite his struggle with Parkinson's disease, he proved his mental alertness by speaking for 20 minutes in French, German and Italian.
He said today's common celebration of the Holy Trinity by all Christians was an urgent summons to move towards unity, and repeated Rome's wish to advance along this difficult but joyful path.
The Pope said that all Catholics would contribute strongly to the cause of Christian Unity if they were more united among themselves.
