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.