For more than four decades, the Roman Catholic Church (search) has followed both the rules and reality concerning gay priests.

The Vatican — as far back as 1961 — has made it clear they are not wanted. But many seminaries continued to tolerate what one conservative theologian calls a "lavender subculture" (search) that's brought perhaps thousands of homosexual men to ordination.

Now those parallel worlds are coming under new and uncomfortable scrutiny.

The Vatican is putting the finishing touches on a document that strengthens its view that gay orientation and the priesthood are essentially incompatible. But the text — which could be released as early as next month — reportedly will not impose a blanket ban on gay priests. Instead, it may demand years of chastity before entering seminary and prohibit any public acts deemed to support the sexually active gay community.

If true, the Congregation for Catholic Education (search) will be mostly bolstering existing Vatican positions rather than shutting the door completely on gay clerics as many liberal Catholics have feared. The question then becomes: What message is the Vatican hoping to send?

Experts in church policies don't expect widespread purges of gay clerics (search) from parishes, schools and seminaries. Many places — particularly in Europe and the United States — are suffering under priest shortages and couldn't risk further losses.

What's more likely, they say, is that bishops will gain new leverage to dismiss or sideline clergymen considered in open defiance of the document. Also, the Vatican statement may serve as a foundation for much more intensive screening of seminary candidates to try to identify — and possibly reject or discourage — those who are gay.

"It could end up restricting entry into the priesthood to heterosexuals, which is a de facto extension of the existing teachings," said R. Scott Appleby, a professor of religious history at the University of Notre Dame. "Even worse, it would place homosexuals into the position of hiding their orientation, lying and suppressing their identity or not entering the church."

Even some conservative Catholics wonder whether the church could become bogged down in internal contradictions from its own rules: If a priest remains celibate and loyal to other Catholic tenets, why does his sexual orientation matter?

"This is where it gets very tricky," said the Rev. Richard John Neuhaus, editor of the New York-based religious and public affairs journal First Things.

He sees the upcoming document as an attempt to curb "a growing influence of gay lifestyles, or what's been called a lavender subculture" in seminaries and other church institutions.

But this can indirectly strike at one of the core elements of the Catholic priesthood — the belief that the call for a vocation can come to anyone. Estimates of the number of gays in U.S. seminaries and the priesthood range from 25 percent to 50 percent, according to the Rev. Donald Cozzens, a former seminary rector and author of "The Changing Face of the Priesthood." Credible global statistics are not available.

"There can be little doubt that over the centuries that there have been great priests, bishops — and maybe even popes — who by today's criterion would be deemed homosexual in orientation," Neuhaus said. "It's not the nature of one's temptations — be they sexual or something else — it's how to deal with these temptations."

No place is this more an issue for church leaders than in the United States, where the nation's bishops were launching a new campaign Friday to attract seminarians.

The sex abuse scandals have forced an unprecedented introspection into the clergy and how to train future priests.

In September, Vatican-directed inspectors started visiting all 229 American seminaries. Part of their mission is to seek any "evidence of homosexuality" at a time when some Catholics have put forward the highly contested premise that gay priests were more likely to be responsible for criminal behavior such as serial, same-sex molestations.

Archbishop Edwin O'Brien, who leads the U.S. military archdiocese and is coordinating the seminary evaluations, strongly opposes any openings for gays in the priesthood.

But apparently the document will offer some avenues — however narrow — for gay priests.

Earlier this month, a senior Vatican official said the document may allow gay men into seminaries if they have lived a chaste life for at least three years. Other possible stipulations reportedly being discussed include forbidding gay seminarians or priests from making public comments or acts that would draw attention to their sexual orientation.

Bishop William Skylstad, the president of the U.S. Conference of Catholic Bishops, said that he was heartened by reports indicating that the document may be "much more nuanced" and "far more sensible" than an outright ban.

The Vatican has often visited the issue of homosexuality, reflecting an unbending theological opposition but also an acknowledgment that discrimination based in sexual preference is not justified.

A key document from 1961 said homosexuals should be barred from the priesthood. In 2003, homosexuality was described as a "troubling moral and social phenomenon" in a document by the powerful Congregation for the Doctrine of the Faith, then headed by German Cardinal Joseph Ratzinger, who became Pope Benedict XVI this year.

Vatican teaching also holds that homosexuals are "intrinsically disordered." The church, however, says gays and lesbians should be treated with compassion and dignity.

Declining vocations and relaxing the rules on priestly celibacy are among the main topics among 250 bishops and other prelates from around the world gathered at the Vatican to examine various aspects of the Catholic Mass and make recommendations to the pope. The three-week meeting wraps up Oct. 23.

But synod participants say the document on gay priests has been barely mentioned — reflecting the imbalance between the intense interest in the United States and limited impact in other regions.

"In the synod, nobody is talking about that," the Rev. Josep Maria Abella Battle, superior general of the Missionary Sons of the Immaculate Heart of Mary. "I know in America there is a lot of worry."