The government of President Barack Obama asked the U.S. Supreme Court on Saturday to find unconstitutional the federal law that defines marriage as "the union of one man and one woman" when it rules on the issue next June.

The Justice Department gave the Supreme Court the first of a series of legal opinions on gay marriage, which the high court must consider now that it has agreed to hear two cases on the subject.

One of the cases questions the constitutionality of the 1996 Defense of Marriage Act, or DOMA, which defines marriage as "the union of one man and one woman," and which Obama has publicly opposed on numerous occasions.

U.S. Solicitor General Donald Verrilli objects in his brief that the law denies same-sex couples a series of federal benefits available to opposite-sex marriages.

The Obama government also considers intervening in the second gay marriage case to be heard by the Supreme Court with regard to California's Proposition 8, which declares gay marriages illegal in that state and was passed by referendum in 2008, soon after the state legalized those unions.

The ban was declared unconstitutional by a court of appeals in 2010, but has now been taken to the Supreme Court its defenders.

Gay marriage is legal in nine states of the union - Maryland, Washington, Maine, New York, Connecticut, Iowa, Massachusetts, New Hampshire, Vermont - and in the District of Columbia.

Another five states allow civil unions, but that is not a right recognized by the federal government.

Last May Barack Obama becames the first U.S. president to publicly support gay marriage.

According to a December survey by USA Today and Gallup, 53 percent of Americans believe that same-sex couples should be able to marry, almost double the percentage supporting gay marriage in 1996. EFE