Administration officials say the Justice Department will urge the U.S. Supreme Court to allow same-sex marriage to resume in California, wading into the protracted legal battle over Proposition 8 and giving gay-rights advocates a new court ally.

After first suggesting it would not get involved, the Obama administration will file a friend-of-the-court brief late today in support of the two gay couples who launched the fight over the issue four years ago, the officials said. Today is the last day for filing briefs in support of the couples' position.

The administration last year signaled it might stay on the sidelines. In May, when President Obama first said that "same-sex couples should be able to get married," he added that it was not a matter for the federal government.

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But he appeared to express a different view in January during his inaugural address when he said, "Our 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."

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The Supreme Court hears oral arguments in late March to decide the fate of Proposition 8, an amendment to the state constitution approved by 52 percent of California voters in 2008. It banned same-sex marriages in the state and went into effect after 18,000 gay couples were legally married earlier that year.