WASHINGTON — The Obama administration is quietly considering urging the Supreme Court to overturn California’s ban on gay marriage, a step that would mark a political victory for advocates of same-sex unions and a deepening commitment by President Barack Obama to rights for gay couples.

Obama raised expectations among opponents of the Proposition 8 ban when he declared in last month’s inaugural address that gays and lesbians must be “treated like anyone else under the law.” The administration has until Feb. 28 to intervene in the case by filing a “friend of the court” brief.

The Proposition 8 ballot initiative was approved by California voters in 2008 and overturned a state Supreme Court decision allowing gay marriage. Twenty-nine other states have constitutional amendments banning gay marriage, while nine states and Washington, D.C., recognize same-sex marriage.

An administration brief alone is unlikely to sway the Justices but the federal government’s opinion does carry weight with the court. A final decision on whether to file a brief has not been made, a senior administration official said. While the Justice Department would formally make the filing, the president himself is almost certain to make the ultimate decision on whether to file.

The Supreme Court, which will take up the case on March 26, has several options for its eventual ruling. Among them:

The justices could uphold the state ban on gay marriage and say citizens of a state have the right to make that call.

The court could endorse an appeals court ruling that would make same-sex marriage legal in California but apply only to that state.

The court could issue a broader ruling that would apply to California and seven other states: Delaware, Hawaii, Illinois, Nevada, New Jersey, Oregon and Rhode Island. In those states, gay couples can join in civil unions that have all the benefits of marriage but cannot be married.

The broadest ruling would be one that says the Constitution forbids states from banning same-sex unions.