WASHINGTON - The US Supreme Court on Wednesday authorised same-sex marriages to be held in Kansas, the 33rd state of 50 where it is legal, in addition to the federal capital Washington.
The high court rejected Kansas' request that it block same-sex marriages in the state, allowing them to proceed.
Only conservative justices, Antonin Scalia and Clarence Thomas, opposed the measure, court documents show.
Last month, President Barack Obama's government said same-sex marriage was recognised in six new US states, increasing the total to 32 plus the District of Columbia.
If Kansas appeals again, in a federal appeal court, it is unlikely to have the case accepted since that court already has shot down identical efforts by two states, Oklahoma and Utah.
The 34th state could be South Carolina; a federal judge there on Wednesday ruled that it was unconstitutional for same-sex marriages to be banned. But that case will be appealed as well.
Last week an appeals court in the US for the first time upheld a ban on same-sex marriage, bucking a trend and likely sending the issue back to the nation's highest court.
The decision by the US Court of Appeals for the Sixth Circuit determined the US Constitution did not prohibit states from defining marriage as between one man and one woman.
The appeals court covers four states in the middle of the country: Michigan, Ohio, Tennessee and Kentucky.
The decision runs counter to a trend of US courts on all levels ruling in favour of same-sex marriages.