Gov. Martin O'Malley sets gay marriage bill signing for Thursday

Maryland Gov. Martin O'Malley.

ANNAPOLIS, Md. (AP) - Maryland Gov. Martin O'Malley will sign a bill legalizing gay marriage next week.

The governor is scheduled to sign the legislation in a 5 p.m. ceremony Thursday, making Maryland the eighth state to legalize same-sex unions.

Opponents have vowed to bring the measure to referendum on the November ballot and began the petition process Friday, a day after the state Senate approved it in a 25 to 22 vote.

They will need to collect 55,736 valid signatures of Maryland voters to put it on the ballot.

Gay marriage advocates said they will fight to make sure the law is upheld and that they think it is inappropriate to leave the issue to the discretion of voters.