The U.S. state of Maryland is a step closer to legalizing same-sex marriage. It would join seven other states and the District of Columbia that currently allow the unions.

The Maryland state Senate Thursday approved a gay marriage bill by a vote of 25-22, days after the measure passed in the state assembly. Maryland Governor Martin O'Malley, a Democrat who sponsored the bill, has pledged to sign it into law.

Opponents say they will gather signatures to bring the issue to a referendum, giving voters a chance define marriage in Maryland.

Referendums in a number of states, including California, have gone against gay marriage, but nationwide polls indicate public sentiment may be shifting.

Earlier this month, New Jersey lawmakers approved a gay marriage bill, but state governor Chris Christie vetoed it. He said voters should decide whether to legalize same-sex marriages.

Supporters in New Jersey's Democratic-controlled legislature have two years to gain the necessary support to override the veto. They currently lack the votes.

Gay marriage is legal in Washington state, Connecticut, Iowa, Massachusetts, New Hampshire, New York, Vermont and Washington, D.C.

A federal appeals court in California ruled just last week that a 2008 referendum that banned gay marriage in that state was unconstitutional.