Far from falling behind on gay rights, US ambassador John Berry believes Australia has been a lighthouse shining the way for campaigners in his country.
Mr Berry says the light from Australia always shone strongly during his decades of fighting for gay rights.
"Much of the advance that we have been able to achieve in the United States has been built following the light that you all have given to us," he told a cross-party group of politicians in Canberra on Monday.
Australian Greens senator Sarah Hanson-Young, co-chair of the group, said it often felt like Australia was falling behind on gay issues.
But Mr Berry said that no country pursuing equality under law was behind.
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He praised Australian sporting codes which have pledged to stamp out discrimination based on sexuality, saying he wished US leagues would take the same "very brave stance".
The ambassador would not weigh into the domestic debate about legalising same-sex marriage but did speak of his personal experience in marrying his partner of 17 years Curtis Yee in 2013.
"We tend to think of love ... as running through daisies and it's all the fun, easy stuff," he said.
"I would say love is best defined in the toughest times."
Mr Berry spoke at Parliament House as MPs took part in a short debate on a private bill legalising same-sex marriage.
Veteran Liberal MP Phillip Ruddock criticised Labor for introducing without proper consultation a private bill which aims to remove legal restrictions on marriage being between a man and a woman.
He urged Labor to withdraw the bill leader Bill Shorten introduced a fortnight ago and instead talk to coalition supporters of gay marriage, like him, about better options.
"It's extremely disappointing to me and my colleagues that Labor took the approach it did," he told parliament.
Meanwhile, anti-gay marriage figures within the government have reportedly circulated polling showing it would lose at least three, but potentially five, Senate seats if the coalition lost the preferences of family and Christian parties because it allowed a conscience vote on the issue.
But the latest Fairfax-Ipsos poll finds nearly seven in 10 Australians support legalising same-sex marriage.
