Pope Benedict XVI delivered a strong defense of Christian marriage on Sunday, urging couples to resist modern cultural currents inspired only by a search for happiness and pleasure.

"May Christian couples build a family that is open to life and capable of handling united the many, complex challenges of our times," Benedict said as he delivered his traditional Sunday blessing from his window overlooking St. Peter's Square.

"There is a need for families who won't let themselves be swept away by modern cultural currents that are inspired by hedonism and relativism," the pontiff added.

Benedict has made the defense of traditional family values a major goal of his papacy and has often challenged moral relativism, or the view that there are no absolute values.

The Catholic Church opposes divorce and other challenges to church doctrine that have become increasingly common in Europe and elsewhere.

The Vatican also has consistently criticized movements in Italy and other countries that call for legal rights for unmarried couples as an attack against the traditional family.

The pope in his speech quoted the words of Jesus in saying that married couples are "two in one flesh."

"The truth about marriage dated back to the beginning of creation, when God ... created them as man and woman," he said.

The pontiff has declared gay marriage to be the "greatest threat ever" to the traditional family based on marriage between a man and a woman.