NSW Labor has delayed a vote on the issue of same-sex marriage until the party's national conference in December.
Delegates at NSW Labor annual state conference in Sydney on Sunday were due to vote on whether to adopt a policy supporting same-sex marriage.
But before debate got under way, NSW Labor general secretary Sam Dastyari tabled a motion asking that the issue be taken to the party's national conference, which will be held in Sydney.
The initial motion was supported by NSW upper house MP Penny Sharpe, Australian Workers' Union national secretary Paul Howes and federal Transport Minister Anthony Albanese, among others.
Mr Howes and Mr Albanese both said they personally supported marriage equality.
Ms Sharpe said that if the conference had voted on the issue on Sunday she believed it would have supported same-sex marriage.
Australian Marriage Equality national convener Alex Greenwich said the delay was a setback.
"We know a clear majority of ALP voters, state conferences, and state leaders support reform, but this NSW setback proves the battle is far from over," he said in a statement.
Supporters of the move have until mid-August to share their views with MPs, at which time they will report back to parliament on their electorates' views on the issue.