(Reuters) - The U.S. Supreme Court on Monday declined to decide once and for all whether states can ban gay marriage, a surprise move that will allow gay men and women to marry in five states where same-sex weddings were previously forbidden.

By rejecting appeals in cases involving Virginia, Oklahoma, Utah, Wisconsin and Indiana, the court left intact lower-court rulings that had struck down the bans in those states. But the high court's action means there will be no imminent national ruling on the issue, with litigation in states where gay marriage is still banned likely to continue.

"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," Chad Griffin, president of the gay rights group Human Rights Campaign, said in a statement.

Other states under the jurisdiction of appeals courts that have struck down the bans will also be affected by the Supreme Court's decision, meaning the number of states with gay marriage is likely to quickly jump from 19 to 30. The other states would be North Carolina, West Virginia, South Carolina, Wyoming, Kansas and Colorado.

The court could still take a future case, but its move on Monday is likely to send a strong signal to lower court judges that rulings striking down marriage bans are consistent with the U.S. Constitution.

Gay couples in the affected states may seek to get married immediately, with the chance of chaotic scenes in some parts of the country, because the high court's action means that the appeals court's rulings are no longer on hold.

The high court’s decision not to hear the cases was unexpected because most legal experts believed it 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.

MESSAGE SENT

The issue could still return to the court, but the message sent by the court in declining to hear the matter would be a boost to gay marriage advocates involved in similar litigation in states that still have bans on the books.

Just over a year ago, the justices ruled 5-4 in June 2013 to strike down a key part of a federal law that had restricted the definition of marriage to heterosexual couples for the purpose of federal government benefits.

That decision in the case U.S. v. Windsor led to a series of court rulings favoring gay marriage in numerous states. In a separate case decided on the same day, the justices sidestepped the broader question of whether state bans violated the U.S. Constitution but allowed gay marriage to move forward 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. Politicians, mostly Democrats but also some notable Republicans, have increasingly voiced their support for ending bans.

It was only as recently as 2004 that Massachusetts became the first state to allow gay marriage following a state court ruling the previous year.

In 17 other states, judges have issued rulings in favor of gay marriage - most of which struck down bans - although the prohibitions have remained intact while litigation continues.

State officials defending their bans counter that 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.