( CNN ) The country 's largest Presbyterian denomination has changed its definition of marriage to include gay couples -- though not explicitly . Presbyterian Church ( USA ) approved an amendment to its constitution after most of its 171 presbyteries -- or governing bodies -- voted for it , PC ( USA ) said Tuesday . Before , the definition said marriage was between `` a man and a woman . '' The new definition says , in part , that `` marriage involves a unique commitment between two people , traditionally a man and a woman , to love and support each other for the rest of their lives . '' Already , PC ( USA ) ministers can perform same-sex marriages in states where such marriages are legal , the group said . But no teaching elder or session can be forced to conduct same-sex marriage ceremonies if they do not believe they are appropriate . Not all members supported the decision . In a post on PC ( USA ) 's website , Jean and Robert Gorney accused the church of going against the Bible and threatened to leave . `` We are not to change the Bible , '' their post said . `` I do n't care who disagrees . '' But the Covenant Network of Presbyterians , which says it supports `` a fully inclusive church , '' welcomed the news Tuesday night . `` The change aligns the church 's constitution with a reality that has long been true : Both same-gender and opposite-gender couples have been living in relationships that demonstrate covenant faithfulness , shared discipleship and mutual love , '' the group said . `` We are also aware that the discussion has been a difficult one for many , and that some will feel a deep sense of pain over this decision . The Covenant Network is committed to fostering healthy dialogue and working with those who hold a view different from ours , seeking opportunities for us to model an authentic and productive unity . '' The amendment will take effect on June 21 . CNN 's Daniel Burke contributed to this report .
Presbyterian Church ( USA ) will define marriage as a `` commitment between two people '' The marriage amendment will take effect June 21 .