New Zealand's parliament is set for a final vote on Wednesday to decide whether same-sex marriages can be legalised.
Lawmakers are to vote on a bill that seeks to amend the country's 1955 marriage act.
The bill passed two previous parliamentary votes and has been endorsed by Prime Minister John Key.
Gay rights advocates say this is a milestone for equality despite strong opposition from Christian lobby groups.
Labour MP Louisa Wall, who introduced the legislation, said that the time is right for change.
"Marginalising and discriminating against particular sectors do not benefit society and families," she said.
"It is a simple choice; do we support discriminatory laws or not? I know I don't and hopefully that is true of most of the members of this house."
The reform is expected to pass convincingly after receiving widespread support during the two previous parliamentary debates, says the BBC's Phil Mercer in Sydney.
The change has also been endorsed by a number of celebrities, including an Olympian, a former governor-general and a supermodel.
But not everyone is in favour.
"Our position is that the traditional definition of marriage shouldn't be altered between a man and a woman," Catholic Bishop Barry Jones said.
Lobby group Protect Marriage also continued an online campaign, saying the change will undermine the traditional concept of marriage.