The United States Supreme Court has agreed to rule on the constitutionality of gay marriage.

Early next year the court will hear challenges to the Defense of Marriage Act, which defines marriage as between a man and a woman.

It will also consider a constitutional amendment in California that overturned a state law, known as Proposition 8, allowing gay weddings.

The court is likely to hear the cases in March next year and a ruling could be issued in June.

Same-sex marriage is a politically-sensitive issue in a country where 31 of the 50 states have passed constitutional amendments banning it.

Washington, DC, and nine states have legalised it, three of them on US election day last month.

Yet even where it is legal, married same-sex couples do not qualify for a host of federal benefits because the 1996 Defense of Marriage Act, or DOMA, passed by the US Congress.

DOMA only recognises marriages between a man and a woman.

Homosexual couples married under state laws have filed suits challenging their denial of such benefits as social security survivor payments and the right to file joint federal tax returns.

They argue the provision, known as Section 3, violates equal protection provisions of the US Constitution.

Meeting in private yesterday at their last weekly conference before the Supreme Court's holiday recess, the justices considered requests to review seven cases dealing with same-sex relationships.

Five of them were challenges to the federal marriage law, one to California's gay marriage ban and another to an Arizona law against domestic partner benefits.