A coalition of some 50 prominent religious leaders, including six Catholic cardinals and six archbishops, have signed a petition and pledged to support a constitutional amendment blocking same-sex marriage, reported the New York Times.

The petition also included prominent evangelical Protestants, a few rabbis and an official from the Church of Jesus Christ of Latter Day Saints.

Matt Daniels, founder of the Alliance for Marriage, an umbrella group that supports an amendment, told the Times that the members of the religious groups represent "huge numbers" of people.

The group has committed to distributing postcards or letters to their congregants to send to senators urging support for the amendment. At the request of the U.S. Conference of Catholic Bishops, the Knights of Columbus printed 10 million postcards addressed to U.S. senators that they are distributing to Catholic churches around the country.

Republican Senate leaders have scheduled a vote in June on the proposed constitutional amendment, and Catholic officials seem more directly involved in this debate than when the amendment was debated in 2004.

Ohio and other pivotal states have already amended their constitutions regarding marriage, but one survey has suggested that the public's opposition is cooling, reported the Times.

In May, a nonpartisan Pew Research Poll found that 51 percent of the public opposed legalizing gay marriage, down from 63 percent in February 2004.