Resolution sponsor Rep. Eric Turner of Marion said he wouldn't call it for a vote on Monday because some House members who want to support it were absent for the day. He didn't specify when he expected a vote.

Political analysts expect that the ban is almost certain to pass, with Republicans in control of the Legislature.

The amendment states that only marriage between one man and one woman is valid in Indiana, and prohibits civil unions by stating that a legal status "substantially similar" to marriage for unmarried people is not valid.

Opponents have argued that the amendment isn't needed because Indiana law already bans gay marriage, but supporters said they are concerned that the courts could overturn that law.

Supporters also contend that traditional heterosexual marriage is best for raising children. Opponents said the amendment seeks to write discrimination into the state's constitution.

Constitutional amendments must go through two separate legislatures before being put to a public vote.

In 2005, the Republican-controlled General Assembly passed a similar amendment, but when Democrats won control of the house in 2006, the proposal didn't clear that chamber a second time.

If legislators pass the measure this year, it would still have to pass again in 2013 or 2014 before it would go on the ballot.

Gov. Mitch Daniels said last year that he wanted legislators to focus on economic and educational reforms in the session and shy away from a social agenda, but he later backed away from that stance.