WASHINGTON (Reuters) - Maryland's same sex marriage proposal was shelved on Friday, in a setback for gay rights supporters who expected this legislative session to be their best chance to date for passage.

After two hours of debate by the full House of Delegates, the Civil Marriage Protection Act was returned to the committee where it was mired last week.

Gay rights supporters anticipated success this year in a handful of states -- Maryland, New York and Rhode Island -- due largely to newly elected lawmakers expected to tip the balance in favor of making gay marriage legal.

Maryland legislators on Friday, however, dashed those hopes. In a spirited debate, many African American delegates said they felt pressured to act according to the wishes of their constituency, including black churches opposed to using the word "marriage" to describe same-sex relationships.

"It turns a moral wrong into a civil right," said Democratic delegate Emmett Burns, Jr..

The chairman of the Judiciary Committee, Joseph Vallario, offered the motion to return the bill to his committee.

"I don't think there has ever been an issue, in the 37 years I have been down here, that has brought more attention, that has had more input from your citizens and from your church," said Vallario.

The leader of minority Republicans, Anthony O'Donnell, said that some form of same sex marriage bill may come up again this year but he did not expect to hear much until next year.

The Senate passed the controversial bill last month. Its journey through the House has been marked by fits and starts. Two co-sponsors of the bill delayed the committee vote needed to bring the bill before the full House.

Democratic Governor Martin O'Malley has publicly supported the bill.

Debate in the Assembly centered around the status of gay marriage as a civil right.

Two amendments were offered, one to allow the issue to be resolved by a referendum of voters and the other to change the language of the proposed law to civil union instead of marriage. Both were rejected.

Seven openly homosexual delegates personally appealed to their colleagues to pass the bill.

Mary Washington, a newly elected delegate and an African-American lesbian, addressed her black colleagues.

"The bridge that is offered that is civil union is a bridge that takes us nowhere. There was no bridge out of slavery." Washington said.

Bill sponsor Jill Carter, a Democratic delegate, blamed its demise on a failure by the Democratic leadership to properly manage the debate.

"The fact that leadership was unwilling to entertain any real debate or discussion within committee, I think that killed it," Carter said.

(Reporting by Wendell Marsh; Editing by Barbara Goldberg and Greg McCune)