A Vermont legislator plans to introduce a bill to allow gay marriage in the state that first approved civil unions for same-sex couples.

State Sen. John Campbell, a Democrat, says he will sponsor the bill in the legislative session beginning in January. He acknowledges it is unlikely to gain ground unless Gov. Jim Douglas signals support.

The Republican governor said Thursday that the civil union law is sufficient but wouldn't say whether he would veto a gay-marriage bill.

Only Massachusetts and Connecticut allow gay marriage. California voters recently overturned a ruling allowing the practice there. Several other states sanction domestic partnerships or civil unions. Vermont became the first state to do so, in 2000.