SAN FRANCISCO — A federal appeals court is expected to announce Tuesday whether it will rehear the case concerning the constitutionality of Proposition 8, California’s voter-approved ban on same-sex marriage.

In February, a three-judge panel of the 9th U.S. Circuit Court of Appeals ruled the measure unconstitutional. In a split decision, the panel found that Proposition 8 “works a meaningful harm to gays and lesbians” by denying their right to civil marriage in violation of the 14th Amendment.

But backers of the proposition have asked for a larger panel of judges to rehear the case. If the appeals court decides to rehear it, oral arguments would be held in the coming months.

If the court declines to rehear the panel’s decision, supporters of the ban could appeal to the U.S. Supreme Court — something they have previously said they are willing to do.

The February three-judge appeals court panel ruling upheld a 2010 decision by a U.S. district judge in San Francisco. However, in the appeals court decision, Circuit Judges Stephen Reinhardt and Michael Daly Hawkins said that they were speaking only to Proposition 8, and that states would have to decide the marriage issue themselves.

California’s Supreme Court ruled that same-sex marriages were legal in 2008, before Proposition 8 went before voters. After the measure passed with 52% of the vote that year, its passage put an end to the practice.

Last month, a federal appeals court in Massachusetts struck down a key part of the Defense of Marriage Act — the law banning federal recognition of same-sex marriage — as unconstitutional. The issue before the 1st U.S. Circuit Court of Appeals was whether the federal government could deny tax, health and pension benefits to same-sex couples in states where they can legally marry. The Massachusetts case could also soon be appealed to the U.S. Supreme Court.

Currently, same-sex marriage is legal in six states: Massachusetts, Connecticut, Iowa, Vermont, New Hampshire and New York, along with the District of Columbia. Washington and Maryland voted earlier this year to allow same-sex marriages, but the laws have not yet taken effect.

Another five states — Delaware, Hawaii, Illinois, New Jersey and Rhode Island — allow civil unions, providing state-level spousal rights to same-sex couples.

Last month, President Barack Obama, who previously opposed same-sex marriage, said that he now supports it.

“When I think about those soldiers or airmen or Marines or sailors who are out there fighting on my behalf and yet feel constrained, even now that ‘don’t ask, don’t tell’ is gone, because they are not able to commit themselves in a marriage, at a certain point I’ve just concluded that for me personally, it is important for me to go ahead and affirm that I think same-sex couples should be able to get married,” the president told ABC.

The National Association for the Advancement of Colored People also announced last month that it supports same-sex marriage.

— CNN’s Bill Mears contributed to this report.