President Barack Obama's administration will urge the U.S. Supreme Court to overturn California's Proposition 8, which barred new same-sex unions in the Golden State, NBC and CNN said Thursday.

The Justice Department is planning to file a friend-of-the-court brief in the case late on Thursday, the networks said.

Last Friday, Justice delivered to the Supreme Court a legal opinion in which it deemed unconstitutional the federal 1996 Defense of Marriage Act, which defines marriage as the union of a man and a woman.

The DOMA is the focus of one of the two cases that the high court will begin reviewing in March, while the other is related to Prop 8, an amendment to the state constitution that was approved in a referendum in 2008, shortly after the state legalized homosexual unions.

In 2010, a federal appeals court declared the amendment unconstitutional, and subsequently Prop 8 supporters decided to take the case to the Supreme Court.

If the Supremes uphold the appellate ruling, gay marriage will once again be legal in California.

On Wednesday, about 200 companies, among them Microsoft, Google and Citigroup, urged the Supreme Court to abolish both the DOMA and Prop 8.

In addition, more than 80 prominent Republicans have expressed their support for same-sex marriage.

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

Civil unions are permitted in five other states.

Last May, Obama became the first U.S. president to publicly support gay marriage. EFE