WASHINGTON — Setting the stage for a potentially historic ruling, the Supreme Court says it will decide whether same-sex couples nationwide have a right to marry under the Constitution.

The justices said Friday they will review an appellate ruling that upheld bans on same-sex unions in four states.

The case will be argued in April and a decision is expected by late June.

Kentucky, Michigan, Ohio and Tennessee are among the 14 states where gay and lesbian couples are not allowed to marry.

The number of states that permit same-sex marriage has nearly doubled in three months as a result of federal and state court rulings. The justices’ decision last October to turn away same-sex marriage appeals allowed some of those rulings to take effect. Florida last week became the 36th state to issue marriage licenses to same-sex couples.

The court is extending the time it usually allots for argument from an hour to two-and-a-half hours. The justices will consider two related questions. The first is whether the Constitution requires states to issue marriage licenses to same-sex couples. The other is whether states must recognize same-sex marriages performed elsewhere.

The appeals before the court come from gay and lesbian plaintiffs in Kentucky, Michigan, Ohio and Tennessee. The federal appeals court that oversees those four states upheld their same-sex marriage bans in November, reversing pro-gay rights rulings of federal judges in all four states.

Ten other states also prohibit such unions. In Arkansas, Mississippi, Missouri, South Dakota and Texas, judges have struck down anti-gay marriage laws, but they remain in effect pending appeals. In Missouri, same-sex couples can marry in St. Louis and Kansas City only.

Louisiana is the only other state that has seen its gay marriage ban upheld by a federal judge. There have been no rulings on lawsuits in Alabama, Georgia, Nebraska and North Dakota.