The bill would ensure that same-sex and interracial marriages are enshrined in US federal law.
The US Senate has passed a landmark bill that would enshrine same-sex and interracial marriages in federal law.
The bill will repeal previous laws that defined marriage as a union between a man and a woman, and also prevents registrars from discriminating against couples "because of their sex, race, ethnicity, or origin".
There were fears that the US Supreme Court might overturn a 2015 ruling that recognises same-sex marriages across the country, following the decision on abortion rights and Roe vs Wade.
Some Republican lawmakers still oppose the legislation, saying it is unnecessary and infringes religious rights.
But the bill was passed on Tuesday by 61 votes to 36, including by 12 Republican senators.
"The United States is about to reaffirm a fundamental truth: love is love and Americans should be able to marry the person they love," US President Joe Biden said in a statement.
The bill is expected to be formally approved by the US House of Representatives next week and then be "promptly and proudly" signed by Biden
Around 568,000 married same-sex couples live in the United States, according to the US Census Bureau.