BOB ABERNETHY, anchor: The debate over gay marriage heated up on several fronts this week. The Vatican launched a new global campaign against same-sex unions, saying homosexual behavior is "against the natural moral law." In a new 12-page document, Vatican officials told Catholic politicians that support of same-sex unions is "gravely immoral." The document also opposed adoptions by gays.

In Washington, President Bush weighed in on the subject. At a Rose Garden press conference, the president urged tolerance for gays. But he also supported the traditional view of marriage.

Meanwhile, more and more gay American couples are heading to Canada to get married. Two Canadian provinces legalized gay marriage in June. But the U.S. public remains conflicted about the issue. As we reported last week, a poll by the Pew Forum conducted at the end of June showed that opposition to gay marriage dropped 10 percent since 1996. However, a new CNN-USA TODAY-Gallup poll found that an increasing number of Americans, almost half, believe homosexual acts should be illegal.

The U.S. Episcopal Church is locked in a battle over a similar issue -- not gay marriage, but the blessing of same-sex unions. It's part of a critical showdown over gay issues that many fear could lead to a major church split. Nearly 800 local church representatives and 300 bishops arrived in Minneapolis this week for the denomination's 10-day-long triennial convention. At the top of their agenda: whether to confirm the church's first openly gay bishop, and whether to develop liturgies to bless same-sex unions. Conservatives say movement on either front will provoke "a dramatic realignment" in the Episcopal Church and in the worldwide Anglican Communion. Kim Lawton reports.

KIM LAWTON: At a downtown chapel in Minneapolis, the worship is exuberant, sometimes emotional, as conservative Episcopalians praise the Lord -- and pray for the future of their church. Most gathered at this service are from the evangelical wing of the U.S. Episcopal Church. They believe the Bible clearly condemns homosexuality, and they're deeply worried about where their church is headed. They feel a sacred obligation to uphold traditional church teaching.

Canon DAVID ANDERSON (American Anglican Council, in sermon): The test is not to be successful in the worldly sense, by winning a vote or whatever. The test is to be faithful, to be obedient to Jesus Christ our Lord.

LAWTON: Canon David Anderson heads the American Anglican Council, an umbrella group of conservative Episcopalians.

Canon ANDERSON: I think the future of the Episcopal Church and even the future of the Anglican Communion is at stake. This is a point at which I think history pivots.

LAWTON: In Santa Barbara, California, members of Trinity Episcopal Church are also concerned about the future. They interpret Scripture more liberally and believe gays and lesbians should be fully incorporated into all aspects of church life. Trinity's rector, Reverend Mark Asman, is himself gay. He says this is a defining moment for all gay and lesbian Episcopalians.

Rev. MARK ASMAN (Trinity Episcopal Church, Santa Barbara): The church has the power to make a decision about where we stand at the table and how welcome we are at the table.

LAWTON: The two very different views have coexisted in the Episcopal Church for decades -- albeit uneasily. But now, many observers wonder how long coexistence can last.

DAVID EARLE ANDERSON (Religion News Service): The alienation of the two sides on this is very profound and very deep -- virtually unprecedented. And it has probably led to -- it's certainly the church's biggest crisis in decades, and perhaps since Henry VIII and the split from Rome.

LAWTON: The Episcopal Church -- George Washington's church -- is one of the oldest denominations in America. And it is poised to make history again. While most other mainline denominations continue to debate the role of gays in the church, in the next few days, Episcopalians may confirm the church's first openly gay bishop, Gene Robinson, who was elected in New Hampshire. And they may approve development of liturgies to bless same-sex unions.

Mr. ANDERSON: It would put them at least two steps ahead on that issue of where most other denominations are now.

LAWTON: That's what worries conservatives such as Canon David Anderson.

Canon ANDERSON: It would represent a departure from established Christian doctrine. God revealed to his people what his intention for human life was and how we are to live. And that has come down, and I don't think God has changed his mind or become better educated.

LAWTON: But other church leaders say biblical injunctions against homosexuality must be interpreted in a contemporary cultural context. Bishop John Bryson Chane of Washington, D.C. says church teaching should be set by a combination of Scripture, tradition -- and reason.