The Obama administration is asking the Supreme Court to overturn California's ban on gay marriage and take a sceptical view of similar bans elsewhere, wading into a case that could have broad implications for the right of same-sex couples to wed.
The administration said unequivocally in a friend-of-the-court brief that gay marriage should be allowed to resume in California, where citizens voted to bar it in a 2008 referendum known as Proposition 8.
It does not explicitly call for marriage equality across the United States, but points the court in that direction.
More immediately, the administration's position, if adopted by the court, probably would result in gay marriage becoming legal in seven other states that, like California, give gay couples all the benefits of marriage, but don't allow them to wed.
They are: Delaware, Hawaii, Illinois, Nevada, New Jersey, Oregon and Rhode Island.
The brief marks President Barack Obama's most expansive view of the legal rights of gays and lesbians to marry. He announced his personal support for gay marriage last year but has said the issue should be governed by states.
Obama, a former constitutional law professor, raised expectations that he would back a broad brief during his inauguration address on January 21. He said the nation's journey "is not complete until our gay brothers and sisters are treated like anyone else under the law".
"For if we are truly created equal, then surely the love we commit to one another must be equal as well," Mr Obama said.
The Justice Department planned to submit its brief later on Thursday (NZT Friday) – the deadline for filing in the California case. The justices will hear oral arguments in the case on March 26.