Maryland Senator Barbara Mikulski on Thursday announced she will co-sponsor a bill that would repeal the Defense of Marriage Act (DOMA), which forbids federal agencies from recognizing the legal marriages of gay and lesbian couples.

Last month, Freedom to Marry presented Mikulski with a petition signed by more than 3,000 people urging the senator to back the bill.

Mikulski announced her decision on Facebook and Twitter.

“I am proud to co-sponsor legislation to repeal key provisions of the Defense of Marriage Act,” Mikulski told gay weekly the Washington Blade. “I believe all Americans are entitled to equal protection under the law and all of our citizens deserve to be treated with dignity and respect.”

Gay marriage supporters believe a Maryland delegation united in favor of DOMA repeal would assist in passage of a state marriage equality bill to be introduced by Governor Martin O'Malley during next year's legislative session, which begins in January. Senator Benjamin Cardin, Maryland's junior senator, co-sponsored the legislation in May.

(Related: Martin O'Malley on gay marriage bill: I think it should pass.)