The statement from Bishop Wilton Gregory was the first from the American church backing a specific amendment that would deny recognition of same-sex marriages.
In a letter this week to his fellow bishops, Gregory wrote that the Senate leadership had asked them to "formally register support" for the legislation.
Introduced by Sen. Wayne Allard, R-Colo., the measure defines marriage as "the union of a man and a woman" and is expected to come before the Senate around July 12.
Gregory asked bishops to urge their senators to get behind the amendment, and to encourage priests and parishioners to do the same.
"This situation challenges Catholics -- and all who seek the truth -- to think deeply about the meaning of marriage, its purposes and its value to individuals, families and society," Gregory wrote.
SOURCE: "Top bishop endorses gay marriage ban" Associated Press. June 26, 2004.