(A same-sex couple marries in New York, June 20, 2012. REUTERS/Adrees Latif )

The U.S. Presbyterian Church on Friday narrowly rejected a proposal by same-sex marriage proponents for a constitutional change that would redefine marriage as a union between “two people,” rather than between a woman and a man.

The 338-308 vote followed nearly four hours of heated debate at the Church’s General Assembly in Pittsburgh, a biennial gathering to review policy.

The Church, with around 2 million members, currently allows ministers to bless gay unions but prohibits them from solemnizing homosexual civil marriages.

Opponents of the change argued the move would alienate the Church from Presbyterian churches in other countries, while backers said it should be a leader in advocating for the acceptance of same-sex marriage.

Michael Wilson, of Lancaster, Pennsylvania, told the General Assembly the proposal threatened to “tear the Church apart.”