Pope Benedict on Friday denounced the "powerful political and cultural currents" seeking to legalize gay marriage in the United States, urging visiting US bishops to beef up their teaching about the evils of premarital sex and cohabitation.

The pope's latest comments in opposition to same-sex marriage came in an address to bishops from several Midwestern states on a regular visit to the Vatican, Reuters reported.

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

Last week, Maryland became the eighth state to legalize same-sex marriage.

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Massachusetts, Iowa, Vermont, New Hampshire, Connecticut, New York and the District of Columbia also allow gay and lesbian weddings, according to the Los Angeles Times.

Washington State will join the list in June unless opponents stop it ahead of a possible referendum, Reuters reported.

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Gay marriage is legal in a number of European countries, including Spain and the Netherlands, according to Reuters.

The 84-year-old Benedict acknowledged his comments might sound anachronistic or "countercultural," particularly to the young. But he told bishops to not back down in the face of "powerful political and cultural currents seeking to alter the legal definition of marriage," The Associated Press reported.

He also denounced what he called the failure of priests and bishops to instruct Catholics in core church teachings on human sexuality, saying many Catholics seem unaware that living together outside of marriage was "gravely sinful, not to mention damaging to the stability of society," according to the AP.

The entire Christian community, he said, must recover an appreciation of the virtue of chastity, the AP reported.

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