ST. LOUIS — The United Methodist Church on Tuesday voted to strengthen its ban on gay and lesbian clergy and same-sex marriages, a decision that could split the nation’s second-largest Protestant church.

After three days of intense debate at a conference in St. Louis, the vote by church officials and lay members from around the world doubled down on current church policy, which states that “the practice of homosexuality is incompatible with Christian teaching.” The vote served as a rejection of a push by progressive members and leaders to open the church to lesbian, gay, bisexual and transgender people.

Now, a divide of the United Methodist Church, which has 12 million members worldwide, appears imminent. Some pastors and bishops in the United States are already talking about leaving the denomination and possibly creating a new alliance for gay-friendly churches.

“It is time for another movement,” the Rev. Mike Slaughter, pastor emeritus of Ginghamsburg Church in Ohio, said in a phone interview from the floor of the conference. “We don’t even know what that is yet, but it is something new.”