Barack Obama's administration has asked the US Supreme Court to overturn California's ban on same-sex marriage and take a sceptical view of similar bans elsewhere, making a historic argument for gay rights.

The administration's friend-of-the-court brief marked the first time a US 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 a 2008 ballot measure that barred gays and lesbians from wedding in California. It does not explicitly call for marriage equality across the United States, but points the court in that direction.

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 do not allow them to wed.

They are Delaware, Hawaii, Illinois, Nevada, New Jersey, Oregon and Rhode Island.

The brief marks President 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.

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.

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.

Mr 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, than surely the love we commit to one another must be equal as well," he said.

Mr Obama has a complicated history on gay marriage. As a presidential candidate in 2008, he opposed the California ban but did not endorse gay marriage. He later said his personal views on gay marriage were "evolving".

When he ran for re-election last year, he announced his personal support for same-sex marriage, but said marriage was an issue that states, not the government, should decide.

American public opinion has shifted in support of gay marriage in recent years.

In May 2008 Gallup found that 56% of Americans felt same-sex marriages should not be recognised by the law as valid. By last November, 53% felt they should be legally recognised.

The Justice Department was submitting its brief on the deadline for filing in the California case. The justices will hear oral arguments in the case on March 26.

The Proposition 8 ballot initiative was approved by California voters in 2008 in response to a state Supreme Court decision that had allowed gay marriage. Twenty-nine other states have constitutional amendments banning gay marriage; nine states and the Washington federal district recognise same-sex marriage.

In recent days, many states, organisations and individuals have filed briefs in the case.

Thirteen states, including four that do not now permit gay couples to wed, urged the court yesterday to declare the ban unconstitutional. They said marriage enhanced economic security and emotional well-being for the partners and was better for children.

"All of these interests are furthered by ending the exclusion of same-sex couples from the institution," said the brief signed by Massachusetts attorney general Martha Coakley.

It was joined by Connecticut, Iowa, Maine, Maryland, New Hampshire, New York, Vermont, Washington, Delaware, Illinois, New Mexico, Oregon and the District of Columbia.

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