Australian rugby star Israel Folau says he does not support gay marriage.
He tweeted his comments as Aussies begin receiving their postal ballots on legalising gay marriage.
Folau, a devout Christian, wrote "I love and respect all people for who they are and their opinions. but personally, I will not support gay marriage."
The ARU have joined the NRL and Cricket Australia in supporting the 'yes' campaign, changing their social media logo to a rainbow Wallaby.
Folau's stance appears to be at direct odds to comments from Wallabies captain Michael Hooper.
"For a lot of guys, they're about footy and our job is rugby, but sport has ability to cross boundaries," Hooper told The Canberra Times.
"We're all very supportive of the 'yes' campaign and this is the approach we've taken."
Unlike New Zealand, the United States and Canada, Australia stands out as a developed, English-speaking country that has not legalised same-sex marriage.
More than 16 million registered voters among Australia's population of 24 million will receive ballots in the coming days requesting their opinion on whether same-sex couples should be allowed to wed.
Most same-sex marriage advocates have condemned the 122 million Australian dollar ($98 million) postal survey as a waste of money and want the Parliament to reform the law without delay.
An Ipsos poll published in Fairfax Media newspapers on Tuesday found 65 percent of respondents said they were certain to take part in the survey.
Of those certain to post their ballot papers back, 70 percent said they would support gay marriage.
If the postal survey finds most Australians want gay marriage, the Parliament will vote by December on legislation to lift the prohibition on gay marriage. But several lawmakers have said they would vote against gay marriage regardless of public opinion.
The Ipsos poll was based on a survey of 1,400 voters between Wednesday and Saturday last week. It had a 2.6 percentage point margin of error.
The result was consistent with previous polls in recent years which have shown around two-thirds of Australians support gay marriage.
But a similar proportion also want legal protections for churches' rights to refuse to marry same-sex couples and to teach that marriage should be between a man and woman.
Critics of the government's approach have argued that the public should see how these rights would be protected in proposed legislation before they decide whether gay marriage should go ahead.
But the government refuses to release a draft bill until after the survey decides whether the Parliament will consider change.
Conservative Prime Minister Malcolm Turnbull and center-left Labor Party opposition leader Bill Shorten are both campaigning for law reform.
But two past conservative prime ministers, Tony Abbott, who remains a government lawmaker, and John Howard, both oppose the change.
The government and opposition are negotiating on details of legislation to be passed by Parliament this week that would penalize campaigners who resort to hate speech during the two-month survey.
Labor lawmaker Penny Wong, who has children with her same-sex partner, told her party colleagues "hurtful and inaccurate" words had already been used.
"This bill won't protect against all of the hate speech we already see. It will provide some limited protection," Wong said.
She complains that "no" campaigners have compared children in same-sex relationship families to Australia's so-called Stolen Generations, mixed-race children who were taken from Aboriginal mothers under now discredited government policies aimed at raising them as non-indigenous Australians.
"No" campaigners have companied that "yes" advocates threaten their opponents in an effort to suppress dissent. The traditional marriage camp point to a short-lived online petition demanding that a Sydney doctor be deregistered for appearing in a television advertisement opposing same-sex marriage. They also point to a Catholic bishop being referred to a state anti-discrimination agency over an anti-gay marriage letter he distributed in his dioceses. The discrimination complaint has since been dropped.
Turnbull, the only serving prime minister to attend the Sydney's Gay and Lesbian Mardi Gras, quoted former British Prime Minister David Cameron at a weekend "yes" campaign launch in arguing that conservatives should support gay marriage.
Abbott, whom Turnbull deposed in an internal government leadership ballot in 2015, has described a "no" vote as a vote against political correctness. Abbott is campaigning against his lesbian sister Christine Forster, a Sydney local government councilor and a member of the same conservative party.