Opponents of gay marriage in the state of California have asked the US Supreme Court to uphold a ban on same-sex weddings that was ruled unconstitutional by an appeal court.
A panel of three judges said the ban - a 2008 state constitutional amendment known as Proposition 8 - violated the civil rights of California residents.
In May President Barack Obama said he supported gay couples' right to marry.
The Supreme Court could take up the matter in its October session.
Proposition 8 was approved by 52% of California voters in November 2008, banning gay marriage just months after state lawmakers legalised it. But a court overturned the ban in 2010.
In June 2012, the judges of the 9th US Circuit Court of Appeals upheld that judgement.
'Judicial death sentence'
Lawyers for opponents of gay marriage were widely expected to ask the Supreme Court to consider their arguments in favour of the ban.
If the Supreme Court chooses not to take up the case it would mean same-sex marriages, which have been put on hold in California, could resume.
"The 9th Circuit's error, if left uncorrected, will have widespread and immediate negative consequences," supporters of Proposition 8 wrote in their petition.
"The 9th Circuit's sweeping dismissal of the important societal interests served by the traditional definition of marriage is tantamount to a judicial death sentence for traditional marriage laws throughout the Circuit."
Lawyers representing two gay couples who first challenged the California ban in 2009 have said they will urge the high court to reject it.
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