Maine voters have rejected a law allowing same-sex couples to marry, in a major setback to gay rights advocates hoping the northeastern US state would become the first in the country where voters directly approve gay marriage.

In a closely-fought referendum, 53 percent of voters defeated a law passed by the state legislature in May, while 47 percent voted for the measure, with 87 percent of precincts reporting early on Wednesday.

The outcome from Tuesday's vote made Maine the third US state where voters repealed their local government's move granting same-sex couples the right to marry, following California and Hawaii. Gay marriage has not yet won a popular vote in any US state.

In Washington state, voters seemed on the verge of approving a referendum granting gays the right to civil unions, with early returns showing a razor-thin margin of 51 percent to 49 percent supporting the expanded status.

The federal government and most states do not recognize gay marriage.

A minority of states ? a total of five ? that have moved to issue marriage licenses to same-sex couples have done so through court rulings or votes in the state legislature.

Those states include Connecticut, Iowa, Massachusetts and Vermont. New Hampshire will allow gay marriage starting in January.

Maine's state legislature voted for same-sex marriage but the measure was delayed and brought before a popular referendum after a repeal petition effort.

Five other states and the capital Washington grant domestic partnership or civil union rights to gay couples, and another three grant some statewide rights.

The Maine vote came a year after California passed a controversial constitutional amendment that banned gay marriage.

"Yesterday, hundreds of thousands of Maine voters stood for equality, but in the end, it wasn't enough," said Jesse Connolly, campaign manager for Protect Maine Equality, the leading group seeking to uphold the same-sex marriage law.

But she vowed the fight would go on.

"We're in this for the long haul. For next week, and next month, and next year ? until all Maine families are treated equally," Connolly said. "Because in the end, this has always been about love and family and that will always be something worth fighting for."