WASHINGTON (RNS) Cohabitation, divorce, contraception and same-sex unions are undermining the traditional meaning and purposes of marriage, the nation’s Catholic bishops warn in an upcoming statement.

“We are troubled by the fact that far too many people do not understand what it means to say that marriage — both as a natural institution and a Christian sacrament — is a blessing and gift from God,” the bishops say in a “pastoral letter” to be adopted at next month’s U.S. Conference of Catholic Bishops meeting in Baltimore.

National Catholic Reporter, an independent weekly newspaper, obtained a draft of the 57-page document, entitled “Marriage: Love and Life in the Divine Plan” and posted the document on its Web site on Monday (Oct. 12).

The bishops are expected to offer amendments to the draft when they gather in Baltimore Nov. 16-19. They will also issue a document on reproductive technologies, revise guidelines on end-of-life care, and hear a preliminary report on the causes and contexts of the clergy sex abuse scandal.

Large portions of the bishops’ letter reiterate arguments the church has made for centuries. But it comes as more Americans, including Catholics, are adopting sexual ethics that contradict church teaching. Meanwhile, President Obama last Saturday criticized “outworn arguments and old attitudes” and pledged to fight for gay rights, including same-sex marriage.

Catholics must lean on centuries of church documents and dogma to fight such innovations, particularly gay marriage, the bishops argue in the letter. “The legal recognition of same-sex unions poses a multifaceted threat to the very fabric of society, striking at the very source from which society and culture come…” the letter reads.

Recognizing gay marriage threatens “the intrinsic dignity of every human person, and the common good,” the bishops say.

The bishops also condemn cohabitation and contraception as “intrinsically evil” because they separate the unifying and procreative dimensions of sex.

H. Richard McCord, executive director of the bishops’ Secretariat of Laity, Marriage, Family Life and Youth, said the letter is part of the bishops’ National Pastoral Initiative on Marriage, which began in 2005 and aims to “strengthen marriage as a human institution and as a sacramental reality.”

Pastoral letters from the bishops conference are relatively rare, McCord said, noting that they are often directed at “big subjects” such as war and capitalism. “It is a teaching tool in which the bishops attempt to summarize the relevant and foundational points of Catholic teaching on a particular subject and apply it to certain issues of the day,” he said.

Already, though, the draft has drawn criticism. In an editorial, National Catholic Reporter said the letter “reads as if it was written by someone who has never once engaged in a marriage preparation program, let alone actually ever been married.”