Welcoming 10 new member states to the European Union, Pope John Paul II again underlined the Christian values which he sees as the basis of the bloc's unity.
"Ten countries which through their culture and traditions were and felt European are now part of this union of states," the pope said Sunday.
His remarks were likely to be interpreted as a new plea for Christianity to be explicitly mentioned in the EU's constitution, and as aimed at opposing EU entry by majority Muslim Turkey.
"The unity of the European people, if it is to last, cannot only be economic and political," the pope said in his weekly address.
"The soul of Europe remains unified today thanks to humane and Christian values that they have in common.
"The history of the formation of European nations is tied to evangelising and despite crises of spirituality the continent suffers to this day, its identity would be incomprehensible without Christianity," the pontiff said.
The 83-year-old Polish head of the Roman Catholic Church said Europe "must keep and rediscover its Christian roots to overcome the great challenges of the third millenium: peace, dialogue between cultures and religions."
The pope, who will celebrate his 84th birthday on May 18, appeared tired after a ceremony lasting almost two hours during which he ordained 26 new priests, among them a fellow Pole.
He had difficulty speaking and appeared to show irritation at the level of noise in St Peter's square which prevented him from concentrating. But he read the whole of his address.
The pontiff and mainly Catholic countries such as Ireland, Italy and Poland have been pushing for the preamble to the EU constitution to refer explicitly to a Christian God as being the fount of European civilisation.
But that has run into opposition from avowedly secular EU members such as Belgium and France, amid fears that such a mention could marginalise Europeans of other faiths or atheists.
"It is unlikely in my view that there will be a reference to God in the constitution, but I think the Christian traditions, the Christian values will be recognised," Irish Prime Minister Bertie Ahern said Saturday.
Ahern, the EU's current chairman, hopes to wrap up the constitution at the next summit of EU leaders on June 17-18.
Ten nations in eastern Europe and the Mediterranean -- the Czech Republic, Cyprus, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia -- took their places in the European Union over the weekend.
EU leaders will review Turkey's democratisation progress in December and decide whether to begin membership talks with the mostly Muslim nation of some 70 million people.
Turkey is the only candidate country with which the EU has so far failed to start accession negotiations.