After nearly four hours of debate, the 2 million member Presbyterian Church (USA) narrowly voted down a gay marriage proposal.

At the Church's biennial convention in Pittsburgh, proponents of marriage equality proposed a constitutional change which would expand the definition of marriage to include gay and lesbian couples. Church delegates voted against the measure 338-308, the AP reported.

The Church's Civil Union and Marriage Issues Committee voted in favor of the change on Thursday night.

Opponents warned that the move would create a division between the Church and other more conservative Presbyterian churches outside the U.S., while backers argued that the Church should lead by example.

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

“[T]he Church doesn't ask us to do what others approve of, it asks us to do what is right” said Piper Madison.

Currently, Presbyterian ministers can bless the unions of gay couples so long as ceremonies are not structured as weddings.

At its last convention in Minneapolis, delegates followed the recommendation of its Church Orders and Ministry Committee and voted in favor of allowing non-celibate gay clergy, a policy change decades in the making.

(Related: Scott Anderson ordained Presbyterian Church's first gay minister.)