Pope Benedict XVI has called on U.S. bishops to oppose the legalization of gay marriage, the AFP reported.

In a speech in Rome on Friday to bishops from the United States, Pope Benedict denounced the “powerful political and cultural currents” seeking to make gay marriage legal in the United States. The Holy Father is speaking out after lawmakers in three states – Maryland, New Jersey and Washington – approved gay marriage bills. New Jersey Governor Chris Christie rejected his state's bill, and laws in the other two states are expected to be challenged this fall at the ballot box.

“Sexual differences cannot be dismissed as irrelevant to the definition of marriage,” he said.

He added that the traditional family and the church's definition of marriage had to be “defended from every possible misrepresentation of their true nature.”

“In this regard, particular mention must be made of the powerful political and cultural currents seeking to alter the legal definition of marriage.”

“The contemporary crisis of marriage and the family … has led to grave societal problems bearing an immense human and economic cost,” he added.

Benedict has previously spoken out against the increasing acceptance of gay nuptials in Europe.

The Roman Catholic Church teaches that gay sex is sinful, but identifying as gay or lesbian is not.