Wedding cake is served by activists outside the Portuguese parliament, Friday, Jan. 8 2010, in Lisbon, after lawmakers passed a bill allowing gay marriage.
Gay-rights activists are hoping U.S. President Barack Obama's support of same-sex marriage will resonate around the world, helping spur change on an issue that remains controversial in many countries.
Homosexuality remains illegal in much of the world and only 10 countries -- Argentina, Belgium, Canada, Iceland, the Netherlands, Norway, Portugal, Spain, South Africa, and Sweden -- allow same-sex marriage.
A look at stances taken by some other leaders:
Argentina
"I believe it would be a terrible distortion of democracy if the majorities – the actions of those majorities – denied rights to those minorities," President Cristina Kirchner said in 2010 as she pushed for gay marriage. A same-sex marriage bill passed after protests by the Catholic church and a marathon session in the Senate.
Australia
Prime Minister Julia Gillard opposes same-sex marriage. Arguing in 2011 that there are "some important things from our past that need to continue to be part of our present and part of our future," she said: "I do find myself on the conservative side in this question."
Belgium
"Mentalities have changed. There is no longer any reason not to open marriage to people of the same sex," said Justice Minister Marc Verwilghen during a late-night debate before the law was passed.
France
Outgoing president Nicolas Sarkozy pledged to modify civil unions, still stopping short of full marriage, while the man replacing him next week is expected to push for same-sex marriage once in office.
"Freedom is the ability to let two people in love, regardless of their sexual orientation to unite," president-elect François Hollande said before the election. "Equality is to allow any couple to use the same device without legal discrimination."
Guatemala
During the 2007 presidential election campaign, Álvaro Colom dismissed gay marriage, arguing that "God said 'Adan and Eve,' not 'Adan and Esteban'."
He changed his tune once elected, agreed to support civil unions and offered an apology. "Esteban, I ask you in the name of the Guatemalan state and in my own name to pardon us for centuries of mistreatment and discrimination."
Polls show the people are strongly opposed, though, and there remains no legal recognition of same-sex marriage. Mr. Colom's successor, Otto Pérez Molina, has not championed the issue.
Italy
Silvio Berlusconi, who faced persistent allegations of womanizing, took a strongly moral stance on same-sex marriage. In 2011, the then-president, told a Catholic conference that his government would hold firm.
"Gays will never have marriages equal to traditional family values because there is only one family," he said, adding: "This government will not allow singles or gays to adopt."
New Zealand
New Zealand Prime Minister John Key has broken a long silence on gay marriage and left the door open for making it legal.
In a statement sent to The Associated Press by his press secretary on Thursday, Mr. Key said he is "not personally opposed to gay marriage." He previously declined to publicly state a position.
He added that gay marriage is not currently on the government's agenda. He did not mention Mr. Obama's announcement Wednesday that he now supports same-sex marriage.
South Africa
In 2006, shortly before same-sex marriage was legalized, presidential hopeful Jacob Zuma called it "a disgrace to the nation and to God" and suggested that, as a young man, he would have assaulted gays bold enough to stand near him. He apologized after protests flared and stressed his recognition of "the sterling contribution of many gay and lesbian compatriots in the struggle that brought about our freedom," as well as their continuing role in building a successful country.
Mr. Zuma became president in 2007. Two years later, following reports that Mr. Zuma was open to considering changes to the same-sex marriage law, his spokesperson said that he would "uphold the Constitution."
United Kingdom
Prime Minister David Cameron, who is believed to be wary of riling the traditional wing of his party, has voiced personal support for gay marriage.
"Conservatives believe in the ties that bind us; that society is stronger when we make vows to each other and support each other," he told a party conference in October of 2011. "So I don't support gay marriage despite being a Conservative. I support gay marriage because I'm a Conservative."
United States of America
''The president believes that marriage is an institution between a man and a woman,'' Ari Fleischer, spokesman for then US president George W. Bush, told reporters in 2003.
The next year, Mr. Bush backed a constitutional amendment that would bar gay marriage but stipulated it should leave "the state legislatures free to make their own choices in defining legal arrangements other than marriage."
In 2009, former US vice-president Dick Cheney, whose daughter was in a long-term same-sex relationship, said that "people ought to be free to enter into any kind of union they wish, any kind of arrangement they wish."
With a report from Associated Press
Oliver Moore