By Edith Honan

NEW YORK (Reuters) - Midwestern minister Greg Smith is considering an act of ecclesiastical disobedience.

Deeply sympathetic to gay rights since his son, Matty, came out as gay a decade ago, the lifelong Presbyterian told his son he will officiate at his wedding, defying church policy.

"I believe that we're doing more harm than good prolonging the inevitable," said Smith, who at 64 is retired but still ministers in Des Moines, Iowa.

"On this issue, there is no mechanism for pastors to express conscientious objection without either defying church authority or demitting from one's pastoral call. And that's extremely stressful and distressing."

Like many other denominations, the Presbyterian Church(U.S.A.), the 10th largest U.S. religion according to the National Council of Churches, is in the grips of a crisis over gay marriage.

The 2.7-million-strong church has lost about 500,000 members over the last decade, and church leaders fear that an endorsement of same-sex marriage could spur an exodus of Christians who view it as incompatible with biblical teachings.

But failing to act could mean the church is viewed as irrelevant and homophobic by young and progressive members.

Earlier this month at its General Assembly, a gathering held every two years, church leaders rejected a constitutional change, by a vote of 338-308, that would have defined marriage as between two people, rather than a man and a woman.

Some have said the church was moving too fast. Just two years ago, the church agreed to open the ranks of its clergy to homosexuals, prompting dozens of congregations to split off to join more conservative denominations or to form their own.

"The Assembly was trying to hold together a broken church with both hands, trying to honor people on both ends of the spectrum who feel pain around the issues of marriage," said Reverend Aimee Moiso, who led the assembly's committee on marriage.

"But we did manage something miraculous: In a polarized church and nation, we spent several days trying to figure out a way to stay together across our divisions," she said.

The Presbyterian Church allows ministers to bless same-sex unions but prohibits them from solemnizing legal homosexual marriages. In February, the church's highest ecclesiastical court upheld the censure of Reverend Jane Spahr for performing 16 same-sex marriages in California.

"Shall we follow the culture, or shall we follow the Bible? That is the dividing line," Carmen Fowler LaBerge, president of the conservative Presbyterian Lay Committee, said this month.

PASTORAL QUANDARY

The legalization of marriage in six states and the District of Columbia, along with the growing visibility of gay parishioners, has put pressure on U.S. churches to reconsider their strict definition of marriage.

Just days after the Presbyterian assembly, the Episcopal Church held its own convention, where the church approved a liturgy for blessing same-sex unions.

"I think it's the same conversation that's going on in society, as people have more relationships with people who are LGBT and they have to wrestle with all these issues," said Reverend Gradye Parsons, a Presbyterian leader, using the acronym for gay, lesbian, bisexual and transgender. Continued...