Officials in Washington state on Tuesday announced that a referendum on a gay marriage law has qualified for the ballot.

The secretary of state's office announced that backers of Referendum 74 had submitted sufficient valid signatures to qualify the question, the AP reported.

Preserve Marriage Washington turned in 247,331 voter signatures last week, more than twice the number needed. Officials checked a random 3 percent sample of signatures for validity.

The marriage law, which was approve by lawmakers at the urging of Governor Chris Gregoire, was set to take effect on Thursday but it was put on hold when the group turned in the signatures last Wednesday.

Opponents of the law said from the start that they would work to defeat the measure, if approved by lawmakers.

Groups are preparing to battle on the issue in 4 states this fall, including Minnesota and Maryland. Voters in Maine will be asked to approve equal marriage rights for gay and lesbian couples.

Various polls have found gay marriage supporters slightly ahead in all four battleground states. Support – in particular among African-American voters and Democrats – has increased since President Barack Obama announced his support for such unions last month.

A recent poll in Washington found that 54 percent of voters believe it should be legal for gay couples to get married.

(Related: Cenk Uygur accuses gay marriage foe Joseph Backholm of hating gays.)