HARRISBURG — The elected official tasked with defending state laws supports same-sex marriage, but now she faces a decision about whether to defend a law that bans it.

State Attorney General Kathleen Kane, the first Democrat to be elected to that position, was scheduled to talk to reporters today at the National Constitution Center in Philadelphia. So far, she has been silent on the first known legal challenge seeking to overturn a 17-year-old law effectively banning same-sex marriage in Pennsylvania, the only northeastern state that doesn’t allow it or civil unions.

The lawsuit, filed Tuesday in federal court in Harrisburg, seeks to make Pennsylvania the 14th state to allow same-sex marriage by asking a federal judge to prevent state officials from stopping gay couples from getting married. Lawyers in the case believe it is ultimately bound for the U.S. Supreme Court, probably along with similar cases that are cropping up in other states, and could force the high court to rule on the core question of whether it is unconstitutional to deny same-sex couples the right to marry.

The lawsuit names as defendants Gov. Tom Corbett, a Republican who opposes gay marriage, and Kane, who said during her campaign last year that she believes gay couples should be able to marry.

Pennsylvania law says it is the attorney general’s duty to defend the constitutionality of state laws. But it also says the attorney general may allow lawyers for the governor’s office or executive branch agencies to defend a lawsuit if it is more efficient or in the state’s best interests.

That means Corbett could end up defending the law in Pennsylvania, where polls show the public is increasingly accepting of the concept of same-sex marriage.