The second-largest Protestant denomination in the country is facing the prospect of mass defections and acts of defiance after delegates at a conference in St. Louis voted Tuesday to strengthen the United Methodist Church's bans on same-sex marriage and the ordination of LGBTQ clergy.

After three days of intense discussions at the General Conference Special Session, 56 percent of the 800 delegates in attendance voted in favor of a proposal by conservatives called Traditional Plan, which upholds the church's stance prohibiting LGBTQ members from being ordained and does not permit same-sex couples to be married.

"It's obviously crushing," delegate J.J. Warren from New York told FOX2. Warren, who is gay and was in the process of becoming ordained, called the vote "incredibly painful."

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The Traditional Plan's success was due to an alliance of conservatives from the U.S. and overseas. About 43 percent of the delegates were from abroad, mostly from Africa, and the overseas delegates overwhelmingly supported the LGBT bans. Membership in the church has been growing in locations such as Africa and Asia.

If the bans were eased, "the church in Africa would cease to exist," said the Rev. Jerry Kulah of Liberia. "We can't do anything but to support the Traditional Plan — it is the biblical plan."

The deep split within the church was evident in several fiery speeches opposing the Traditional Plan.

"If we bring this virus into our church, it will bring illness to us all," said the Rev. Thomas Berlin of Herndon, Virginia. He predicted many Methodist churchgoers and some regional bodies would leave the church, while others would "stay and fight," performing same-sex weddings even if it meant punishment.

Council of Bishops President Kenneth H. Carter, speaking at a news conference after the session, said the meeting in St. Louis was necessary "because if the impasse we found ourselves in" over questions of human sexuality.

"I would just simply say that we have work to do. We did not accomplish that in these three days," Carter said. He added he was concerned the plan will cause progressive churches to leave the denomination.

"Persons will feel harmed," he said.

Formed in a merger in 1968, the United Methodist Church claims about 12.6 million members worldwide, including nearly 7 million in the United States. High-profile church members include former Attorney General Jeff Sessions, ex-Secretary of State Hillary Clinton and former first lady Laura Bush. After the vote was complete, dozens of people filled the lobby outside the convention hall at the Dome at America's Center to sing, pray and support one another, FOX2 reported.

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While other mainline Protestant denominations, such as the Episcopal and Presbyterian (U.S.A.) churches, have embraced gay-friendly practices, the Methodist church still bans them, though acts of defiance by pro-LGBTQ clergy have increased. Many have performed same-sex weddings; others have come out as gay or lesbian from the pulpit of their churches. Enforcement of the bans has been inconsistent, but that could change under the Traditional Plan.

The Rev. Tim Bagwell, 64, pastor at a UMC church in Macon, Georgia, had opposed the Traditional Plan and called the outcome "deeply painful." But he said his church will stay with UMC until at least 2020, when the next major conference is scheduled. He's hopeful new delegates will be elected and change course to a more inclusive church.

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"I am deeply sad," he told the Associated Press. "The Methodist church has always been mainstream, reaching out to people. This sends a different tone...one of exclusion, not inclusion."

The Associated Press contributed to this report.