July 16 (Reuters) - An 83-year-old lesbian asked the Supreme Court on Monday to hear her legal challenge against a federal law that defines marriage as a union between a man and woman, contending it denies equal protection for married same-sex couples.

The suit, filed by Edith Schlain Windsor in 2010, targets the Defense of Marriage Act, a law passed by the U.S. Congress in 1996 that denies federal benefits to lawfully married same-sex couples.

Windsor's petition attempts to place her case on the fast track to the Supreme Court by bypassing the U.S. Court of Appeals for the 2nd Circuit, which is slated to hear the case in September. With Windsor's filing there are currently three petitions pending before the Supreme Court over the constitutionality of DOMA, an issue the high court could take up in oral arguments as early as next spring, said Windsor's lawyer, Roberta Kaplan of Paul, Weiss, Rifkind, Wharton & Garrison.

"This case presents a question of exceptional national importance: the constitutionality of a statute, the Defense of Marriage Act ('DOMA'), that daily affects the lives of thousands of Americans," the petition said.

The American Civil Liberties Union originally filed the suit in New York on behalf of Windsor, a former IBM computer programmer who married her late spouse, Thea Clara Spyer, in Toronto, Canada, in 2007. The two were engaged in 1967.

Spyer died in 2009 after a decades-long battle with multiple sclerosis, leaving all of her property to Windsor. Because the marriage was not recognized under federal law, Windsor had to pay more than $363,000 in federal estate taxes, according to the suit.

Six states have legalized same-sex marriage since DOMA went into effect, including New York in 2011. But federal law and programs do not recognize those marriages because of DOMA.

Windsor's attorneys argue that the federal law violates the 14th Amendment of the U.S. Constitution, which prohibits states from denying people equal protection of the laws.

In June, a New York district court ruled in Windsor's favor, finding that a central DOMA provision discriminates against married same-sex couples. The case is now on expedited appeal before the 2nd Circuit. But Windsor's lawyers argue that premature review of her case by the Supreme Court is warranted, given that the issue is already before the high court and that Windsor suffers from a serious heart condition that could end her life before the case is resolved.

Federal courts in New York, California and Massachusetts have all found the law unconstitutional for different reasons, applying varying standards of legal analysis.

The Republican-controlled House of Representatives, through its Bipartisan Legal Advisory Group, is defending the law, which the Obama administration essentially abandoned in 2011. In June, lawyers for BLAG asked the Supreme Court to review a recent decision from the 1st Circuit in Massachusetts v. Department of Health and Human Services, which found the law unconstitutional. The Justice Department has also asked the high court to review another DOMA challenge that's currently pending in the 9th Circuit, Golinski v. Office of Personnel Management.

Paul Clement, a lawyer for BLAG, did not immediately respond to a request for comment on Windsor's petition.

The case before the 2nd Circuit is Windsor v. USA et al, No. 12-2335.

For Windsor: Roberta Kaplan of Paul, Weiss, Rifkind, Wharton & Garrison.

For the Bipartisan Legal Advisory Group: Paul Clement of Bancroft.

(Reporting By Terry Baynes)

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