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Speaking at the U.S. embassy in London, Kerry said, "As long as a marriage has been performed in the jurisdiction that recognizes it, then that marriage is valid under U.S. immigration laws. Every married couple will be treated exactly the same, and that is what we believe is appropriate."

He continued: "If you are the spouse of a U.S. citizen, your visa application will be treated equally. If you are the spouse of a non-citizen, your visa application will be treated equally. If you are in a country that doesn't recognize your same-sex marriage, then your visa application will still be treated equally at every single one of our 222 visa processing centers around the world." 

The move comes after the U.S. Supreme Court struck down a law against same-sex marriage in June. 

SEE ALSO: Supreme Court Strikes Down DOMA And Dismisses Prop. 8

According to gay rights advocates, the measure will mostly affect married gay couples overseas as spouses can apply to join each other if one of them already has a visa. 

U.S. immigration law requires visa travel documents for those who want to live in the United States permanently or to stay temporarily.

See U.S. Department of State policy change here. 

Reach Executive Producer Syuzanna Petrosyan here. Follow her on Twitter.