A plan to unify four Protestant denominations after a 450-year rift survived a heated debate over homosexuality and gay clergy on Wednesday as the smallest church became the first to approve the agreement.

The Reformed Church in America overwhelmingly urged “full communion” with the 5.2-million member Evangelical Lutheran Church of America, allowing joint congregations, minister exchanges and shared sacraments for the first time since the 16th century.

“This will be heard around the world,” said Wesley Granberg-Michaelson, general secretary of the nearly 400,000-member church. “It is a historic moment, a faithful step towards the unity that already exists in Christ.”

If approved, the plan would build closer ties among nearly 10 million Protestants.

The rift stemmed from disagreements among leaders of the Reformation, when the Protestant denominations split from the Roman Catholic Church in the 16th century.

Some delegates worried that the agreement gave indirect support to the United Church of Christ’s policy of ordaining homosexual ministers.

Granberg-Michaelson tried to reassure delegates that the issue of homosexuality and gay clergy was separated from the unity plan.

The Evangelical Lutheran Church, the 1.5-million member United Church of Christ and the 2.7-million member Presbyterian Church USA will vote this summer.