The Human Rights Campaign (HRC), the nation's largest gay rights advocate, has begun a campaign urging the GOP-led House not to defend the Defense of Marriage Act (DOMA), the Clinton-era law that bans federal agencies from recognizing the legal marriages of gay and lesbian couples and allows states to ignore such marriages from other states.

President Barack Obama said last week that he believes parts of the law are unconstitutional, which prompted Republican House leaders to announce they would defend the law in court.

HRC's online petition urges lawmakers to repeal the law, not defend it: “Congress should be focused on helping Americans, not hurting them, I ask you to reject any attempts by Republican leaders to waste taxpayer dollars on defending this unconstitutional law in court.”

“We're all prepared for [Republicans] to intervene in some way,” Michael Cole-Schwartz, an HRC spokesman, told “The question is how do they do it, how do they roll it out, and what kind of political hay they want to make of it?”

House Majority Leader Eric Cantor on Monday joined House Speaker John Boehner in promising action to defend the 15-year-old law. Cantor said lawmakers would respond on how they planned to fill the legal void on Friday.