"Today I am proud to announce that the critical programs for veterans and elderly and disabled Americans, which previously could not give effect to the marriages of couples living in states that did not recognise those marriages, will now provide federal recognition for all marriages nationwide," US Attorney General Loretta Lynch said.
The announcement comes after a Supreme Court ruling in this regard last month that legalised same-sex marriage.
A year ago, the then Attorney General Eric Holder had announced that agencies across the federal government had implemented the Supreme Court's Windsor decision by treating married same-sex couples the same as married opposite-sex couples to the greatest extent possible under the law as it then stood.
"With the Supreme Court's new ruling that the Constitution requires marriage equality, we have now taken the further step of ensuring that all federal benefits will be available equally to married couples in all 50 states, the district of Columbia and the US Territories," Lynch said.