Recognition of same-sex marriages in the US will be expanded to all federal courtrooms and prisons, ensuring gay couples receive the same benefits as heterosexuals.
The move, which Attorney General Eric Holder announced on Saturday at a gay rights dinner gala in New York, marks a major gain for advocates of same-sex couples after the Supreme Court issued two rulings expanding gay marriage rights last year.
Under the new policy, same-sex couples will enjoy the privileges even in states that do not recognise their marriages, so long as they legally wed in another state.
Among the benefits extended to same-sex couples are the compensation fund for the September 11, 2001, attacks, as well as death and educational benefits for the surviving spouses of police officers and firefighters injured or killed in the line of duty.
Same-sex couples would also be held to the same legal standard as their heterosexual counterparts on matters such as how debts are handled in federal bankruptcy proceedings and visitation policies at federal prisons, as well as compassionate release or sentence reductions in certain cases of crisis involving their spouse.
Advocates of gay rights hailed the decision.
"This landmark announcement will change the lives of countless committed gay and lesbian couples for the better," said Chad Griffin, president of Human Rights Campaign, whose gala was the site of Holder's speech.
"While the immediate effect of these policy decisions is that all married gay couples will be treated equally under the law, the long-term effects are more profound.
"Today, our nation moves closer towards its ideals of equality and fairness for all."
But conservatives blasted the decision, suggesting President Barack Obama's administration had chosen a liberal interpretation of the Supreme Court rulings.
