(CNN) -- The Maryland Senate voted Thursday evening to legalize same-sex marriage, the latest sign of growing national recognition of such unions among gay and lesbian couples.

Gov. Martin O'Malley has pledged to sign the bill into law, which was approved last week by the House of Delegates.

"All children deserve the opportunity to live in a loving, caring, committed, and stable home, protected equally under the law," O'Malley said in a statement after the vote.

The Maryland vote comes less than two weeks after Washington legislators voted to legalize same-sex marriage. That measure will take effect in the summer if it survives a likely court challenge.

Six states and the District of Columbia already issue same-sex marriage licenses -- Connecticut, Iowa, Massachusetts, New Hampshire, New York and Vermont. Five states -- Delaware, Hawaii, Illinois, New Jersey and Rhode Island -- allow civil unions that provide rights similar to marriage.

New Jersey lawmakers approved same-sex marriage this month, but Gov. Chris Christie vetoed the legislation. He has said voters should decide the issue in a statewide referendum.

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