Voters in the US state of Maryland now narrowly support allowing gay couples to marry, a survey suggests.

The Washington Post poll of 1,030 adults, taken last week, found that 46 per cent support allowing same-sex marriage, compared to 44 per cent against and ten per cent who said they had no opinion.

In 2007, an identical poll question by the newspaper found 44 per cent in favor overall and 51 per cent opposed.

On the question of whether Maryland should recognise same-sex marriages performed in other states, 55 per cent in the latest survey agreed while 38 per cent disagreed.

Maryland law states that only a man and a woman can be married. Couples can gain some equal rights but as there is no state register of partnerships, they must provide a sworn affidavit along with two other legal documents such as evidence of a joint mortgage or bank account.

In February, Attorney General Douglas Gansler told state agencies to grant gay couples who married in other states the same rights as heterosexual couples.