WASHINGTON — In a historic argument for gay rights, President Barack Obama on Thursday urged the Supreme Court to overturn California's same-sex marriage ban and turn a skeptical eye on similar prohibitions across the country.

The Obama administration's friend-of-the-court brief marked the first time a U.S. president has urged the high court to expand the right of gays and lesbians to wed. The filing unequivocally calls on the justices to strike down California's Proposition 8 ballot measure, although it stops short of the soaring rhetoric on marriage equality Obama expressed in his inaugural address in January.

California is one of eight states that give gay couples all the benefits of marriage through civil unions or domestic partnership but don't allow them to wed. The denial of marriage to same-sex couples, "particularly where California at the same time grants same-sex partners all the substantive rights of marriage, violates equal protection," the administration said.

The administration's position, if adopted by the court, would likely result in gay marriage becoming legal in the seven other states: Delaware, Hawaii, Illinois, Nevada, New Jersey, Oregon and Rhode Island.

In the longer term, the administration urges the justices to subject laws that discriminate on sexual orientation to more rigorous review than usual, a standard that would imperil other state bans on same-sex marriage.

The brief marks the president's most expansive view of gay marriage and signals that he is moving away from his previous assertion that states should determine their own marriage laws. Obama, a former constitutional law professor, signed off on the administration's legal argument last week following lengthy discussions with Attorney General Eric Holder and Solicitor General Donald Verrilli.