VATICAN CITY (CNS) — Pope Benedict XVI urged American Catholics to strive for greater unity, especially among ethnic groups and between bishops and religious orders, in order to carry out the church’s mission in an increasingly hostile society.

The pope made his remarks May 18 in a speech to U.S. bishops from the Chaldean, Ruthenian, Maronite, Ukrainian, Armenian, Melkite, Syriac and Romanian Catholic churches, who were making their periodic “ad limina” visits to the Vatican. They were the last of 15 groups of U.S. bishops to make to make “ad limina” visits since November 2011, reporting on the status of their dioceses to Pope Benedict and holding discussions with Vatican officials.

In his speech, Pope Benedict called for greater “Catholic unity” to counter the “forces of disaggregation within the church which increasingly represent a grave obstacle to her mission in the United States.”

The pope echoed his earlier warnings to other U.S. bishops about the dangers of secularization and state curbs on religious freedom.

“With the progressive weakening of traditional Christian values, and the threat of a season in which our fidelity to the Gospel may cost us dearly, the truth of Christ needs not only to be understood, articulated and defended, but to be proposed joyfully and confidently as the key to authentic human fulfillment and to the welfare of society as a whole,” he said.