The United Methodist Church’s top legislative assembly convenes Sunday for a high-stakes, three-day meeting likely to determine whether America’s second-largest Protestant denomination will fracture due to divisions over same-sex marriage and the ordination of gay clergy.

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, even though acts of defiance by pro-LGBT clergy have multiplied and talk of a possible breakup of the church has intensified.

At the church’s upcoming General Conference in St. Louis, 864 invited delegates are expected to consider three plans for the church’s future. Several Methodist leaders said they expect a wave of departures from the church regardless of the decision.

“I don’t think there’s any plan where there won’t be some division, and some people will leave,” said David Watson, a dean and professor at United Theological Seminary in Dayton, Ohio, who will be attending the conference.

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. In size, it trails only the Southern Baptist Convention among U.S. Protestant denominations.