VATICAN CITY -- The pope pressed his opposition to gay marriage Friday, denouncing what he described as people manipulating their God-given identities to suit their sexual choices -- and destroying the very "essence of the human creature" in the process.

Benedict XVI made the comments in his annual Christmas address to the Vatican bureaucracy, one of his most important speeches of the year. He dedicated it this year to promoting traditional family values in the face of vocal campaigns in France, the United States, Britain and elsewhere to legalize same-sex marriage.

In his remarks, Benedict quoted the chief rabbi of France, Gilles Bernheim, in saying the campaign for granting gays the right to marry and adopt children was an "attack" on the traditional family made up of a father, mother and children.

"People dispute the idea that they have a nature, given to them by their bodily identity, that serves as a defining element of the human being," he said. "They deny their nature and decide that it is not something previously given to them, but that they make it for themselves.

"The manipulation of nature, which we deplore today where our environment is concerned, now becomes man's fundamental choice where he himself is concerned," he said.

It was the second time in a week that Benedict has taken on the question of gay marriage, which is dividing France, and which scored big electoral wins in the United States last month. In his recently released annual peace message, Benedict said gay marriage, like abortion and euthanasia, is a threat to world peace.

After the peace message was released last week, gay activists staged a small protest in St. Peter's Square.

Church teaching holds that homosexual acts are "intrinsically disordered," though it stresses that gays should be treated with compassion and dignity. As pope and as head of the Vatican's orthodoxy watchdog before that, Benedict has been a strong enforcer of that teaching: One of the first major documents released during his pontificate said men with "deep-seated" homosexual tendencies shouldn't be ordained priests.

For the Vatican, though, the gay marriage issue goes beyond questions of homosexuality, threatening what the church considers to be the bedrock of society: a family based on a man, woman and their children.

In his speech, the pope cited Bernheim as lamenting how a new "philosophy of sexuality" has taken hold, whereby sex and gender are "no longer a given element of nature that man has to accept and personally make sense of: it is a social role that we choose for ourselves, while in the past it was chosen for us by society."

He said God had created man and woman as a specific "duality" -- "an essential aspect of what being human is all about."

Now, though, "Man and woman as created realities, as the nature of the human being, no longer exist. Man calls his own nature into question. From now on he is merely spirit and will."

The Vatican's opposition to gay marriage has been falling largely on deaf ears. Under then-Socialist leader Jose Luis Rodriguez Zapatero, the largely Roman Catholic Spain legalized gay marriage. Three U.S. states approved same-sex marriage by popular vote in November elections. Earlier this month, the British government announced it will introduce a bill next year legalizing gay marriage, though it would ban the Church of England from conducting same-sex ceremonies.

In France, President Francois Hollande has said he would enact his "marriage for everyone" plan within a year of taking office last May. The text will go to parliament next month. But the country has been divided by vocal opposition from religious leaders, prime among them Bernheim, as well as some politicians and parts of rural France.

The Socialist government's plan also envisions legalizing same-sex adoptions. Benedict quoted Bernheim as denouncing the plan, saying that it would mean a child would essentially be considered an object people have a right to obtain.