Episcopal Church considers same-sex blessing service NEW: Policy has been in development since 2009 National convention's House of Bishops has OK'd the policy; House of Deputies votes next Church would become the largest protestant denomination to bless same-sex relationships Church leaders would study the issue for three years before making it permanent (CNN) -- Episcopal priests would be allowed to conduct services blessing same-sex relationships under a policy up for final approval Tuesday at the church's national convention in Indianapolis. The convention's House of Bishops approved the provisional policy 111-41 with three abstentions Monday, clearing it for consideration by the House of Deputies, church media affairs representative Neva Rae Fox said Tuesday. If the proposal is approved, the Episcopal Church would become the largest U.S. denomination to officially sanction same-sex relationships. The Episcopal Church has about 1.95 million members in the United States, down 16% over the last decade, according to the church. The proposed service is not considered a marriage ceremony, media affairs representative Nancy Davidge said. "We have authorized a blessing, and a blessing is different than a marriage," she said. A blessing is a theological response to a monogamous, committed relationship. Marriage requires the additional involvement of civil authorities, and many states do not allow gays to marry. The Episcopal policy calls for a three-year trial run of the blessing service, which is called "The Witnessing and Blessing of a Lifelong Covenant." It would be accompanied by a review process leading up to the church's next annual convention in Salt Lake City. It's then that church leaders would decide whether to make the policy permanent, Fox said. The policy, which has been in development since 2009, allows local bishops to decide whether to allow the service. It also includes a provision stating that clergy members who object to same-sex unions cannot be coerced to perform the blessing, or be disciplined for refusing. As with civil politics, the issue of same-sex marriage has roiled American churches for years. In 2003, the Episcopal Church in the United States split over the election of an openly gay priest, Eugene Robinson, as bishop in New Hampshire. Just this summer, the Presbyterian and Methodist churches also rejected similar measures at their conferences. The United Methodist Church, at its General Conference meeting in Tampa, Florida, upheld the church's position on homosexuality, which excludes gay marriages and same-sex unions. The Methodist body also rejected a proposal saying the church is not of one mind on the issue of homosexuality. This month in Pittsburgh, the General Assembly of the Presbyterian Church USA decided not to change the church's definition of marriage as being "between a man and a woman." Delegates approved a two-year study of the issue. The only major U.S. denomination to endorse same-sex marriage across the board is the United Church of Christ, which did so in 2005. In 2009, the Evangelical Lutheran Church in America allowed member churches to recognize same-sex relationships, but stopped short of creating a church-wide policy or crafting a specific blessing service. During Monday's debate, Bishop Nathan Baxter of Central Pennsylvania said the policy would allow the church to focus on inclusion while respecting theological differences within the church, according to the Episcopal News Service. But others said the policy was a bad idea, the news service reported. "The Christian world is going to understand us as having changed the nature of the sacrament of holy matrimony," the news service quoted Bishop Edward Little of Northern Indiana as saying. The Christian world will look at that liturgy world and see vows, and exchange of rings, a pronouncement and a blessing and they will understand that to mean the Episcopal Church has endorsed same-sex marriage and changed a basic Christian doctrine. I do not believe that we are free to do that. Randall Balmer, a Dartmouth University religion professor and an Episcopal priest who supports the change, said he expects little fallout from the policy, should it be approved. Most of the most conservative Episcopalians who oppose blessing same-sex relationships have probably already left the church, Balmer said. "In many ways, the church is tracking public sentiment," which is increasingly supportive of same-sex relationships, Ballmer said. The Episcopal Chirch is merely part of that trend. CNN's Eric Marrapodi contributed to this report.