By Lawrence Hurley

WASHINGTON (Reuters) - The U.S. Supreme Court declined on Monday to decide once and for all whether states can ban gay marriage, a surprising move that will allow gay men and women to get married in five additional states, with more likely to follow quickly.

On the first day of its new term, the high court without comment rejected appeals in cases involving five states - Virginia, Oklahoma, Utah, Wisconsin and Indiana - that had prohibited gay marriage, leaving intact lower-court rulings striking down those bans.

As a result, the number of states permitting gay marriage would jump from 19 to 24, likely soon to be followed by six more states that are bound by the regional federal appeals court rulings that had struck down other bans. That would leave another 20 states that prohibit same-sex marriage.

But the move by the nine justices to sidestep the contentious issue means there will be no imminent national ruling on the matter, with litigation likely to continue in states with bans.

"Any time same-sex couples are extended marriage equality is something to celebrate, and today is a joyous day for thousands of couples across America who will immediately feel the impact of today's Supreme Court action," said Chad Griffin, president of the gay rights group Human Rights Campaign.

Evan Wolfson, who heads the group Freedom to Marry, said while Monday’s action provided "a bright green light" to gay marriage in more states, gay rights advocates still want the high court to intervene and provide a definitive ruling covering all 50 states. "The Supreme Court should bring the country to a nationwide resolution," Wolfson said.

Officials in states whose bans were overturned had also wanted the high court to decide the matter. The justices could take up a future case, but their move on Monday could send a strong signal to lower court judges that rulings striking down gay marriage bans are consistent with the U.S. Constitution.

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Gay couples in affected states are expected to seek marriage licenses immediately because the high court's action means the appeals court's rulings are no longer on hold. Virginia began issuing licenses within hours of the court's action.

The other states that are likely to be imminently affected are North Carolina, West Virginia, South Carolina, Wyoming, Kansas and Colorado.

NO EXPLANATION

The court did not explain why it was not taking up the issue. Among the possibilities are that a majority believes it would be premature to intervene and wants to see more lower court action, or that on this deeply polarized court neither the liberals nor the conservatives could be certain of how the issue would resolved and did not want to risk forcing a national precedent now.

Justice Ruth Bader Ginsburg, who has officiated at a same-sex wedding, said last month that for the justices there is "no need for us to rush" unless a split emerges in the regional federal appeals courts and one of them decides to uphold a state ban on gay marriage.

In order for the Supreme Court to hear a case, at least four of the nine justices must vote to hear it.

Most legal experts had believed the justices would want to weigh in on a question of national importance that focuses on whether the U.S. Constitution’s guarantee of equal treatment under the law means gay marriage bans were unlawful.

White House spokesman Josh Earnest said that "there may ultimately be a role for the Supreme Court to play" on gay marriage and that the justices must make that call. Earnest emphasized that President Barack Obama's view is that "it's wrong to prevent same-sex couples who are in loving, committed relationships and want to marry from doing so."

Opponents of gay marriage said they would continue to defend state bans in court. "The people should decide this issue, not the courts," said Byron Babione, a lawyer with the conservative Alliance Defending Freedom.

In June 2013, the justices ruled 5-4 to strike down a key part of a federal law called the Defense of Marriage Act that had restricted the definition of marriage to heterosexual couples for the purpose of federal government benefits.

But in a separate case decided that day, the justices also sidestepped the broader question of whether state bans violated the Constitution, but allowed gay marriage in California.

The momentum within America's courts in favor of gay marriage reflects a sea-change in public opinion in the past decade, with polls showing a steady increase in support. It was only as recently as 2004 that Massachusetts became the first state to allow gay marriage following a state court ruling.

State officials defending their bans say the Constitution does not dictate how states should define marriage and that there is no deeply rooted legal tradition that supports a right to gay marriage.

When the nine justices ascended their mahogany bench at 10 a.m., they betrayed no concern for the possible uncertainty or confusion arising from their orders rejecting the same-sex marriage cases. Proceeding with the usual practice, Chief Justice John Roberts announced only that “orders have been duly entered and certified” and were on file with the clerk’s office.

The justices then heard an hour of arguments in a case involving a police search.

(Reporting by Lawrence Hurley; Additional reporting by Joan Biskupic in Washington, Heide Brandes in Oklahoma City and Marti Anne Maguire in Raleigh, North Carolina; Editing by Will Dunham)