The Washington DC council has voted unanimously to recognise gay marriages performed in other states.
Previously, gay couples who were married in other states were recognised as domestic partners when they moved to DC but the measure, it passes a final vote next month, means their unions will be recognised as marriages.
In a statement, DC mayor Adrian Fenty said he looked forward to signing the bill.
The bill will require that married same-sex couples must be accorded the same benefits as those received by married straight couples.
The development comes days after Iowa and Vermont legalised same-sex marriage.