Los Angeles - A US appeals court on Tuesday upheld its decision to strike down a California law banning gay marriage, in the latest step in the dispute's expected path to the Supreme Court.
Opponents of the ban hailed the ruling as a "victory for loving, committed gay and lesbian couples in California and around the nation", while proponents vowed to take the case "promptly" to the nation's top court.
The Ninth Circuit Court of Appeals ruled in February that an amendment to the California state constitution banning same-sex marriage violated principles of due process and equal protection under the law.
Supporters of a ban had asked the San Francisco-based federal court to re-hear the case "en banc" - with 11 judges, as opposed to the three-judge panel which ruled in February.
But on Tuesday's seven-page ruling concluded: "The petition for rehearing en banc is denied."
A group which co-sponsored the challenge to "Prop 8" - the 2008 referendum initiative which imposed the ban - hailed the decision, which opens a 90-day window in which Prop 8 supporters can appeal to the US Supreme Court.
"Today's order is yet another federal court victory for loving, committed gay and lesbian couples in California and around the nation," said Chad Griffin, co-founder of American Foundation for Equal Rights.
Same-sex marriages in California will remain on hold pending a final decision on the dispute.
Pro-Prop 8 lawyer Andy Pugno of ProtectMarriage.com said the ruling was not a surprise.
"We have anticipated since the beginning that the case will ultimately be decided by the United States Supreme Court," he said.
"We will promptly file our appeal to the nation's highest court and look forward to a positive outcome on behalf of the millions of Californians who believe in traditional marriage."
Los Angeles Mayor Antonio Villaraigosa said the ruling was "another momentous step on the path to full equality and dignity for all Californians and all Americans".
"Today we celebrate... Tomorrow we prepare for the hoped-for last chapter in our decades long fight for marriage equality - a ruling by the United States Supreme Court," Villaraigosa said.
"Between now and then, we will continue to make our case. Love doesn't care if you're gay or straight, love doesn't discriminate."
Gay marriage was briefly authorised in California in 2008, but later banned by a referendum on what was known as Proposition 8. It rewrote the state's constitution to restrict marriage to unions between a man and a woman.
The February judgment was slammed by Republican presidential hopeful Mitt Romney, who said "unelected judges [had] cast aside the will of the people of California who voted to protect traditional marriage".
But California Attorney General Kamala Harris called the decision "a victory for fairness, a victory for equality and a victory for justice".
Professor Doug NeJaime of the Loyola Law School in Los Angeles said he does not expect the US Supreme Court to rule on the issue until October at the earliest.
"The Supreme Court will eventually weigh in on this. Now, we just have to wait and see," he said.